More than 600 relatives of UN peacekeepers and other foreigners were evacuated by ship from the southern port city of Tyre, a region south of the Litani that has seen a ferocious pounding by Israeli warplanes and gunboats for days. Many of the women and children had spent the night on the beach waiting for the ship that arrived Thursday morning and took them to Cyprus.

Evacuees from Lebanon are welcomed after their arrival on a special flight from Damascus at Cologne airport July 20, 2006. Three Airbus A-310 planes of the German Air Force Luftwaffe brought 500 evacuees on Thursday from Adana, Turkey, and Damascus, Syria, to Germany. [Reuters]

The exodus of Americans and other foreign nationals stepped up dramatically, with ships lining up off Beirut to take thousands of families waiting at the port out of the war zone.

A group of around 40 US Marines hit the ground in Beirut, helping in the evacuation of hundreds of Americans to a Navy transport vessel, the USS Nashville, offshore, the first US military deployment in Lebanon in 22 years. More than 2,200 Americans were pulled out Thursday, twice the number a day before.

Israeli forces resumed attacks on Beirut at daybreak on Friday, witnesses said. One loud explosion was heard in the Lebanese capital. Al-Arabyia TV said the strike had targeted Beirut's southern suburbs, Hezbollah's stronghold. Israeli strikes Thursday pounded southern Beirut and villages and towns in the Shiite heartland of the south and the eastern Bekaa Valley.

Hezbollah, in turn, fired more than 40 rockets into northern Israel.

The clashes about a mile inside the Lebanese side of the border Thursday evening came when an Israeli patrol sweeping for Hezbollah bunkers was ambushed by guerillas, taking casualties. The fight rapidly expanded, with Israeli helicopters firing missiles at targets on the ground and rescue forces storming in.

The Israeli military said two Israeli soldiers died in the fighting and several guerrillas were killed. Hezbollah's Al-Manar television said three Israeli soldiers were killed but did not mention guerrilla casualties.

Two Apache attack helicopters collided in an accident northern Israel near the Lebanon border early Friday, killing one air force officer and injuring three others, two seriously, Israeli officials said. Al-Jazeera reported that four soldiers were killed in the crash, but did not give a source.

The commander of Israel's air force appointed an inquiry team to determine the cause.

Israel has stepped up its small-scale forays over the border in recent days, seeking Hezbollah positions, rocket stores and bunkers. Each time it has faced tough resistance from the guerrillas.

In preparation for a more powerful punch deeper into Lebanon, an Israeli military radio station that broadcasts into the south issued what it called "a strict warning" that Israeli forces would "act immediately" to halt Hezbollah rocket fire.

"It will act in word and deed inside the villages of the south against these aggressive terrorist acts. Therefore all residents of south Lebanon south of the Litani must leave their areas immediately for their own safety," the message in Arabic on the Al-Mashriq station said.

More than 300,000 people are believed to live south of the Litani, which twice has been the border line for Israeli buffer zones. In 1978, Israel invaded up to the Litani to drive back Palestinian guerrillas, withdrawing from most of the south months later.

Israel invaded Lebanon again in a much bigger operation in June 1982 when its forces seized parts of Beirut. It eventually carved out a buffer zone that stopped at the Litani. That zone was reduced gradually but the Israeli presence lasted for 18 years until 2000, when it withdrew its troops completely from the country.