The details given by Lt. Gen. Dhahi Khalfan Tamim are the most comprehensive accusations by Dubai authorities since the body of Mahmoud al-Mabhouh was found Jan. 20 in his luxury hotel room near Dubai's international airport.
Tamim told reporters the alleged assassination team comprised six British passport holders, three Irish and one each from France and Germany. But he did not directly implicate Israel - . The group has accused Israel's Mossad secret service of carrying out the killing and has pledged to strike back.
Tamim said it was possible that "leaders of certain countries gave orders to their intelligence agents to kill" al-Mabhouh, one of the founders of Hamas' military wing. Israeli officials have accused him of helping smuggle rockets into Gaza.
He said forensic tests indicate al-Mabhouh died of suffocation, but lab analyses are still under way to pinpoint possible other factors in his death.
Top Hamas figures have denied reports that al-Mabhouh was en route to Iran, which is a major Hamas backer. But the group has not given clear reasons for his presence in Dubai.
Tamim sketched out a highly organized operation in the hours before the killing.
He showed a news conference surveillance video of the alleged assassination team arriving on separate flights to Dubai the day before al-Mabhouh was found dead. The suspects checked into separate hotels.
They paid for all expenses in cash and used different mobile phone cards to avoid traces, he added.
At least two suspected members of the hit squad watched al-Mabhouh check in at his hotel and later booked a room across from the Hamas commander, Tamim said.
He added that there was "serious penetration into al-Mabhouh's security prior to his arrival" in Dubai, but that it appeared al-Mabhouh was traveling alone.
"Hamas did not tell us who he was. He was walking around alone," said Tamim. "If he was such an important leader, why didn't he have people escorting him?"
Tamim said there was at least one unsuccessful attempt to break into al-Mabhouh's hotel room. It was unclear whether he opened the door to his killers or if the room was forcibly entered.
The killing took place about five hours after al-Mabhouh arrived at the hotel and all 11 suspects were out of the United Arab Emirates within 19 hours of their arrivals, he added.
Tamim said the suspects left some evidence, but he declined to elaborate. He urged the countries linked to the alleged killers to cooperate with the investigation.
Earlier this month, Hamas said it launched floating explosives into the Mediterranean Sea to drift toward Israeli beaches to avenge al-Mabhouh's death.
Israeli authorities discovered at least two explosives-rigged barrels and carried out an intensive search for other bombs, closing miles of beaches and deploying robotic bomb squads.
A Hamas statement last month acknowledged al-Mabhouh was involved in the kidnapping and killing of two Israeli soldiers in 1989 and said he was still playing a "continuous role in supporting his brothers in the resistance inside the occupied homeland" at the time of his death.
More than 2,000 mourners attended al-Mabhouh's funeral and burial at the Palestinian refugee camp of Yarmouk, near Damascus, Syria.