The international police organization says it has issued red notices, its highest-level alert, for a 16-strong team accused of "closely watching, following and reporting" the movements of Mahmoud al-Mabhouh before his killing.
Interpol said Monday it had issued the alerts at the request of authorities in Dubai, in the United Arab Emirates.
It already has issued red notices for 11 other people suspected in the January killing.
The methodical stalking and killing of al-Mabhouh in a luxury hotel room has been widely blamed on Israel's Mossad spy agency. Israel has neither confirmed nor denied involvement.
Hamas slaying in Dubai ripples worldwide
If there's a signature moment in the plot to kill Mahmoud al-Mabhouh, it's likely his short elevator ride from the hotel lobby to Room 230.
The Hamas commander and a woman hotel clerk enter the elevator and, just before the doors close, two men slip in.
They look like any tourist here for the Persian Gulf winter sunshine: baggy shorts, tennis rackets, sneakers and baseball caps. Al-Mabhouh - still wearing the winter jacket he traveled in from Damascus to Dubai - barely gives them a glance.
But Dubai police say he was rubbing shoulders with two members of a surveillance team that would trail him to identify his room in the Al-Bustan Rotana hotel. A few hours later, authorities say, assassins would break in, drug him with a syringe jab and then smother him with a pillow - a killing Dubai's police chief Lt. Gen. Dahi Khalfan Tamim calls "99 percent, if not 100 percent" carried out by Israel's Mossad secret service.
The tactics might look like old school: simple disguises such as wigs, months of scouting missions and a hotel pillow as the murder weapon. But they are thoroughly modern in one important sense. We're seeing it unfold: on media Web sites and social networks such as Facebook and YouTube - everything but the killing itself.
Perhaps no other political assassination has ever been so quickly and thoroughly displayed before the public, a testimony to the pervasiveness of surveillance technology and our connected world.
Key events surrounding the Jan. 19 killing were captured on hotel security cameras. The body was discovered the next day, but the news didn't become public until nine days later. Then Dubai authorities rushed to release evidence in order to embarrass Israel, which insists it doesn't know who was responsible but has welcomed the killing, claiming al-Mabhouh was a key link in smuggling weapons to Gaza and a possible middleman with Israel's archenemy, Iran.
The accusations hinge on tangible clues: expertly faked passports, many of them linked to apparent identity theft in Israel; credit cards under aliases stretching from banks in Germany to a small town in Iowa; and the surveillance tapes, edited by Dubai police into a kind of 27-minute video indictment for the media.
The swift exposure has put Israel on the defensive. It is being called to answer to its own citizens who had their identities stolen, as well as to allied governments whose passports were abused.
The affair has left a trail of mysteries across the Middle East.
If Mossad was behind it, did it act alone? The slain man's aide has claimed Arab forces hostile to Hamas collaborated in the killing.
How badly damaged was the perpetrating agency by having its methods put on display for the world? There has been criticism even within Israel. "The last assassination of its kind," said a headline in the Israeli daily Haaretz, suggesting it had ended an era of covert operations.
Did the alleged hit squad members push their luck? Did they think the chances of being identified were just too remote? Was it deliberate misdirection, or a lightly veiled warning to other perceived enemies? Al-Mabhouh's aide, Mohammed Nassar told Hamas' Al Aqsa radio in Gaza that his boss was involved in supplying weapons for Hamas, fueling speculation in Israeli media that he was heading for talks on a new arms deal with Iran.
"There's a huge number of questions to be answered," said Mustafa Alani, head of security studies at the Gulf Research Center in Dubai. "But what is rather clear is that someone underestimated the Dubai police."
One of those questions is why it took 10 days for the slaying to be made public. Another is this: Al-Mabhouh, one of the founders of Hamas' armed wing, had survived at least three reported attempts on his life since 1991. So why did he travel alone to Dubai?
Hamas has not offered any clear details. But if there was an Iranian connection, Dubai would be an obvious choice.
It's an important transit point for legal goods to Iran and, some experts say, for military and nuclear-related shipments banned by U.N. sanctions. It supports Hamas in Gaza and Hezbollah in Lebanon, and openly calls for Israel's destruction.
Just hours after Dubai police released the first names and identities of the suspects, a phone rang in the town of Beit Shemesh west of Jerusalem.
It was the first of dozens of calls from reporters to Melvyn Adam Mildiner, who was home recovering from pneumonia.
Did you know your name was mentioned by Dubai police? Is this your passport number? Have you ever been to Dubai?
Mildiner, a dual British-Israeli citizen who emigrated to Israel about a decade ago, first asked if it was a joke. Not at all. It quickly became clear.
The photo on the British passport cited by Dubai police was not him. The birthday was off by a few days, but the passport number was correct. He had his real passport with him.
"Bizarre," said Mildiner. "I have never been to Dubai."
At least 20 men and six women have so far been linked to the plot through falsified passports from Europe or Australia. Most were in logistics and surveillance, scouting out Dubai for at least nine months, police say. Two Palestinians also are in custody.
The passports gave them visa-free access to Dubai, and they followed common routines. They nearly always traveled on Emirates, which uses its own terminal where crowds are generally light and immigration lines move quickly. And they stayed in Dubai no more than a few days on trips beginning as early as March 2009.
The tally by Dubai police: 12 British passports, six Irish, four French, three Australian and one German. A mysterious "27th suspect" is wanted.
At least 15 of the names on the passports are shared by dual citizens living in Israel: a British-born building contractor on a kibbutz. An ultra-orthodox seminary student. A physiotherapist at a Jerusalem hospital.
They are not considered suspects, but could face a travel purgatory as long as their names stay on Interpol watch lists.
"I am just a father, a husband, and a kibbutz resident," pleaded Paul Keeley, whose name was on a passport.
Other Israeli links to the slaying have been raised.
Dubai police claim at least 17 credit cards were issued to the suspects using the faked passports to purchase air tickets and book hotels. Most of the cards were prepaid accounts issued by Meta Financial Group Inc. in Storm Lake, Iowa, a town of 10,000 billed by its Chamber of Commerce as a "welcome relief from hectic city life."
Authorities have in turn linked that bank to Payoneer Inc., which provides prepaid MasterCards issued by MetaBank and other lenders.
The role of privately held Payoneer, which is based in New York and has a research and development center in Tel Aviv, has not been made clear.
The company, founded in 2005, is headed by CEO Yuval Tal. A 2006 Fox News interview identified Tal as a former member of the Israeli special forces. In the interview, Tal provided commentary on the war between Israel and Hezbollah. He described the conflict as one that Israel must win.
"It's a war that they cannot lose. ... The Israelis have to win this war," Tal told the network's "Fox & Friends" program. "It's something that the Israelis knew for many, many years, and I think now the world is understanding better what is going on."
One of Payoneer's main backers, Carmel Ventures, is based in Israel. Other investors include Greylock Partners, which has significant operations in Israel, and Crossbar Capital, whose co-founder previously headed an Israeli venture capital firm.
In 2003, Greylock tapped Moshe Mor, a former Israeli army military intelligence officer, to head its expansion into Israel, according to a press release at the time.
Payoneer is also affiliated with Taglit-Birthright Israel, which organizes educational trips to Israel for groups of young Jewish adults to "strengthen participants' personal Jewish identity." Participants are required to pay trip deposits through the company, according to the group's Web site.
The Associated Press called Payoneer's Tel Aviv office and got a recording listing extensions, but when these were pressed, there was only dead air.
After the slaying, Payoneer said it was cooperating with MetaBank and cooperating in the investigation.Mary Kae Marinac, a spokeswoman for Payoneer, said Monday that Tal was unavailable and that the company "is providing no further comment on the matter."
A statement from MetaBank to the AP said the prepaid credit cards were loaded with funds by outside companies, but gave no further details.
Israel, meanwhile, is facing diplomatic fallout and questions at home.
Australian Foreign minister Stephen Smith said any Israeli role in the faked passports would not be considered the "act of a friend." Last month, Israel's foreign minister, Avigdor Lieberman, sidestepped questions about al-Mabhouh slaying gathering at European Union headquarters.
In Israel, too, there have been some calls for an internal reckoning on Mossad's tactics, though majority opinion seems to hold that the end justifies the means.
Tzipi Livni, leader of the parliamentary opposition and a former Mossad recruit, called the slaying "good news." Trade Minister Binyamin Ben-Eliezer, a former general, said it shows that no one in Hamas is "untouchable" but added: "I don't know if it is us or not."
However, international pressure - and slip-ups - have pried out Israeli disclosures in the past. In 1997, Israel was forced to send an antidote that saved the life of Khaled Mashaal when two Mossad agents posing as Canadian tourists were captured after injecting the Hamas leader with poison.
Dubai police have moved from accusing Israeli officials to taunting them. Dubai police chief Tamim called on Mossad chief Meir Dagan to confirm or deny a role in the killing.
"Let him be a man," Tamim sneered. "Tell the truth."
On Friday he announced that his force has collected suspects' DNA and fingerprints, and confirmed that the assassins managed to leave the room locked from the inside.
Tamim has vowed to block entry to Dubai to anyone suspected of having a second passport from Israel. But how to spot them? By profiling Israeli "physical features" and speech patterns. Tamim didn't elaborate.
Even after pointing his finger at the Mossad, Tamimi also has suggested leaks within Hamas about al-Mabhouh's movements could have been the crucial factor.
Jordanian political analyst Labib Kamhawi said Israel may one day be forced to admit to an "illegitimate act."
"By the same token," he added, "it's a lesson for the Arabs and Palestinian resistance that Palestinian security agencies are infiltrated."
As for Hamas, it has pledged to keep fighting. Mashaal, survivor of the earlier poisoning attempt, addressed Israel directly when he said of Mabhoub's slaying: "You have hurt us with his killing, but it is an ongoing war between us."
PARIS, March 8, 2010