The pre-dawn seizure near Cyprus was a rare interception of a suspected arms shipment by Israel, which has long accused Iran of arming its enemies. Israel offered no evidence to support its claim that the weapons were meant for Hezbollah.
Weapons including anti-tank missiles and Katyusha rockets were stashed on a commercial vessel operating under the guise of an aid ship, captained by a Pole and flying an Antiguan flag, Israeli defense officials said. They spoke on condition of anonymity because the military had not officially released the information.
Based on intelligence reports, a naval unit patrolling the area intercepted and boarded the vessel without incident, defense officials said.
Deputy Defense Minister Matan Vilnai said the crew was not aware of the cargo's contents.
The ship, the Francop, was towed to the southern Israeli port of Ashdod, where the weapons were being unloaded. The vessel is operated by United Feeder Services, a Cyprus-based shipping company that said it picked up the cargo in Damietta, Egypt.
An employee of the company's chartering department who would not identify himself said the ship had been bound from Egypt to Cyprus and from there to Lebanon and Turkey. He said the company did not know what was inside the containers or where the cargo originated.
The employee asked that his name not be used because the company had yet to formulate an official response.
UFS' niche is bringing cargo to small ports not called by big container ships.
A senior Lebanese army official refused to comment on the Israeli report, saying it happened outside Lebanon's national waters. He spoke on condition of anonymity in line with military regulations.
Israeli Defense Minister Ehud Barak called the interception "another success against the relentless attempts to smuggle weapons to bolster terrorist elements threatening Israel's security." Prime Minister Benjamin Netanyahu said the arms supply "was intended to hit Israeli cities."
The vessel was the second major arms ship Israel has seized in its campaign to quash the smuggling of weapons to Palestinian and Lebanese militants.
In January 2002, Israeli forces stormed the Karine A freighter on the Red Sea, and confiscated what the military said was 50 tons of missiles, mortars, rifles and ammunition headed for Palestinian militants in the Gaza Strip.
Authorities from other countries, including the United States last month, have stopped ships suspected of carrying arms in the past.
The Lebanon-Israel border has been largely quiet since Israel and Hezbollah fought a fierce war in the summer of 2006. But Israel has long warned that Hezbollah fighters have been rearming and now possess some 40,000 rockets.
Gaza militants also have dramatically reduced their rocket attacks on southern Israel since a bruising winter war. But militants continue to smuggle in rockets and components through underground tunnels with Egypt, the Israeli military says.
On Tuesday, the head of military intelligence said Gaza's militant Hamas rulers recently test-fired a missile capable of striking Israel's largest urban center, metropolitan Tel Aviv.
Eli Shaked, former Israeli ambassador to Egypt, said the growing arsenals of Hamas and Hezbollah are changing the balance of power between Israel and the Iranian-backed militant groups.
"The situation is becoming more and more complex because the weapons they are acquiring are more and more dangerous to civilian targets in Israel," Shaked said.
The weapon Hamas recently test-fired is "the doomsday weapon" because if such rockets are ever used to attack Tel Aviv, "this will force Israel to start an all-out war."
The presence of Iranian proxies in the Mideast have combined with Tehran's nuclear program and arsenal of long-range missiles to make Iran the Jewish state's most formidable foe.
Israel shares the West's fears that Tehran is developing nuclear weapons, despite its assertions to the contrary. Neutralizing the Iranian nuclear threat remains Netanyahu's top priority and Israel has not ruled out a military strike against Tehran's nuclear facilities.