The Shiite militant group's military wing, the Islamic Resistance, claimed in a statement that its guerrillas had "destroyed a Zionist warship ... off Tyre."

"At 4:30 pm (1330 GMT), the Islamic Resistance attacked with its blessed missiles an Israeli SAAR 4.5 (fast attack missile boat), with a crew of 53 officers and soldiers, off the coast of Tyre," it said.

"It was hit and destroyed.

"This is the begining of the vengeance for the children of Qana."

Hezbollah had vowed revenge following the killing of 52 people, most of them women and children, in an Israeli air raid on the village of Qana on Sunday.

But the Israeli military denied that any of its ships off Lebanon's coast had been targeted with a missile. "The report is simply not true," a spokesman said.

On July 14, just two days after Israel launched its offensive against Lebanon, Hezbollah fired a rocket into a warship off Beirut, killing four Israeli sailors.