Israeli commandos seized a ship Wednesday that defense officials said was carrying hundreds of tons of weapons from Iran bound for Lebanon's Hezbollah guerrillas - the largest arms shipment Israel has ever commandeered.

The Israeli military said an Iranian document was found on board, showing that the arms shipment originated from Iran, although the paper was not shown to reporters. Rear Admiral Roni Ben-Yehuda, the deputy Israeli navy commander, said that despite its size, the shipment of weapons was "a drop in the ocean" of arms being shipped to Hezbollah.

"It's a cargo certificate that shows that it was from a port in Iran," military spokeswoman Lt. Col. Avital Leibovich said. "All the cargo certificates are stamped at the ports of origin, and this one was stamped at an Iranian port."

The Israelis boarded the ship before dawn in the waters near Cyprus. Israel has long accused Iran of arming its enemies.

Ben-Yehuda told a briefing that "hundreds of tons" of weapons were found on the ship, giving a much higher estimate than an earlier one of more than 60 tons.

Containers had Iranian shipping codes in English - "IRISL" on one side and "I.R. Iranian Shipping Lines Group" on the other. Some of the hundreds of crates lined up on the dock were open, revealing dark green missiles with English-language designations painted in black.

But hours after the seizure, Israel had not provided proof that the arms were meant for the Lebanese guerrillas.