A large fight between Israeli forces and Hizbollah guerrillas broke out today evening on the Lebanese side of the border, the Israeli army said, adding that its troops suffered casualties but did not elaborate. Hizbollah’s Al-Manar television said three Israeli soldiers were killed and 10 wounded in fighting.

The forces crossed the border as part of ongoing operations to push back Hizbollah guerrillas who have continued firing rockets into northern Israel despite more than a week of massive bombardment.

Israel, meanwhile, hinted at a full-scale invasion. It warned residents to flee a nearly 32-km swath of south Lebanon along the border. Its warplanes also launched new airstrikes on Beirut’s southern suburbs, a Hizbollah stronghold, shortly after daybreak, followed by strikes in the guerrillas’ heartland in the south and eastern Bekaa Valley.

The planes also bombed large parts of the south, from which Hizbollah guerrillas fired more rockets into Israel. On Wednesday, Israeli bombings killed as many as 70 people, according to Lebanese television, making it the deadliest day since the fighting began July 12.

Late on Wednesday, soon after Lebanon’s prime minister said Israel’s onslaught had ‘‘torn the country to shreds’’, Israeli warplanes dropped 23 tons of bombs on a supposed bunker sheltering the top Hizbollah leader Nasarallah in a south Beirut suburb. Hizbollah issued a statement shortly after saying the destroyed building was a mosque under construction and that it had suffered no casualties.

UN Secretary-General Kofi Annan told the Security Council that “hostilities must stop’’ between Israel and Hezbollah. He also condemned Israel’s “excessive use of force’’ in Lebanon.

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