JERUSALEM - Nineteen soldiers were killed and five others were missing and feared dead as Israeli forces thrust deep into south Lebanon, the army said Sunday, making it the highest one-day toll for the Jewish state since the war against Hezbollah erupted.

The soldiers were killed in a series of battles Saturday as helicopters landed commandos near the Litani River and columns of armor and infantry pushed north to meet them. The deaths brought to more than 100 the number of Israeli troops killed so far.

One of the transport helicopters was shot down by Hezbollah guerillas and its five-man crew was missing and feared dead, the army said.

Israel launched its expanded offensive early Saturday in a bid to seize territory and capture Hezbollah strongholds before the onset of a U.N.-imposed cease-fire.

U.N. Secretary General Kofi Annan said that after talking to Prime Ministers Fuad Saniora of Lebanon and Ehud Olmert of Israel, it was agreed the cease-fire will take effect Monday morning.

"I am happy to announce that the two leaders have agreed that the cessation of hostilities and the end of the fighting will enter into force on 14 August, at 0500 hours GMT," the statement said.

Israel and Lebanon are three hours ahead of GMT.

Israel's Cabinet was to meet later Sunday and expected to accept the U.N. resolution.

Several soldiers were killed when hit by anti-tank missiles and others in fierce gunbattles with the guerillas. Two more were killed when a tank accidentally ran over them, the army said, adding that more than 50 Hezbollah fighters were killed. Israel Radio reported that some 100 soldiers were injured in the clashes.

The helicopter was shot down in the Maryamein valley near the village of Yater. It was Israel's first loss of a helicopter in Lebanon in the monthlong conflict. Two helicopters collided and crashed and a third crashed separately in northern Israel early on in the fighting.

Four hours after the downing of the aircraft, Hezbollah reported a gunbattle was still raging as Israeli troops were trying to retrieve the casualties from the burning wreckage, according to a statement issued by the group.

The claim, carried on Hezbollah's al-Manar TV, said the helicopter was brought down by a new missile, the "Waad" (Arabic for Promise) in the guerrilla arsenal.