With fears of a humanitarian crisis growing, Israel opened up its blockade of Lebanon's ports to allow the first shiploads of aid to arrive, and tens of thousands of Lebanese fled north to escape Israeli army incursions.

Some 35,000 Lebanese filled the southern port town of Sidon as they searched for a place to stay or a way to get farther north. With the town of 100,000 unable to absorb more refugees, many families were joining Palestinians in a refugee camp.

Israel lifted its sea blockade Friday after Israel's U.N. Ambassador Dan Gillerman said his country would open a humanitarian corridor for food, medicine and other supplies.

A Greek warship carrying 22 tons of humanitarian supplies arrived Friday in Beirut, followed Saturday by another with 14 tons of supplies, the Greek Foreign Ministry said. An Italian navy ship was expected the next day.

The next task is to distribute the aid. It was unclear how it would get to isolated towns and villages in the south — the center of the war zone — where main routes and many side roads through the mountains have been cut off by Israeli airstrikes. Missiles and artillery continue to fall in the area, making the roads still dangerous.

Sidon, some 20 miles south of Beirut, has swelled with 35,000 refugees from the south, Mayor Abdul-Rahman al-Bizri said.

A constant stream of cars flowed down the main street through the city. Vegetable markets were open only for several hours before their day's supplies ran out amid the rush to stock up.

"I'm afraid a disaster is going to happen with all these refugees. There's no aid, not from other nations, not from Lebanon," said al-Bizri, who has been sleeping in his office for days as he deals with the crisis.

The Sidon area has largely been spared Israeli bombardment in recent days, but a wave of bombings early in the Israeli offensive shattered the main roads in and out of the city. Sidon is about halfway between Beirut and the port of Tyre, which is the biggest city south of the Litani River and has borne the brunt of severe Israeli strikes.

Refugees have been filling schools in Sidon for days — and by Friday they were full. So the southern Lebanese joined Palestinian refugees in the nearby camp of Ain Hilweh, moving into schools in the camp. Palestinians were supplying them with whatever blankets and foam mattresses they could spare.

Others tried to go north. The main coastal highway has been cut and bridges destroyed — as has the parallel, older Sidon-Beirut route — forcing cars to make their way up winding roads into the Shouf mountains.

Israel has blockaded the ports since its offensive against Lebanon began after the July 12 capture of two Israeli soldiers by Hezbollah guerrillas.

U.N. humanitarian chief Jan Egeland called on Israel to guarantee safe passage for humanitarian goods into northern Lebanon by road; into the ports of Beirut, Tripoli and Tyre for sea cargo; and into Beirut airport for air shipments. The airport has been put out of commission by Israeli strikes on its runways.

It was not clear, however, whether Israel had agreed to define routes inside the country for the aid to be moved from the entry points to the southern villages and towns where tens of thousands are believed still trapped.

Al-Bizri said he had received no word about any international aid headed to Sidon or for arrangements to deliver aid.

The United Nations estimates that more than 500,000 people have been displaced by the Israeli onslaught against the south, the southern neighborhoods of Beirut and the eastern Bekaa Valley, Shiite areas where Hezbollah has strong support.

The flight appeared to be accelerating as Israel warned everyone south of the Litani — 20 miles from the border — to flee north. The region has more than 400,000 people, and some estimates said well over half of them have streamed north.

Hundreds of Israeli troops knocked down a border fence and moved into the Lebanese village of Maroun al-Ras on Saturday, engaging Hezbollah militants as part of the country's limited ground campaign.

Marwaheen and surrounding villages were rapidly emptying, an area of about 6,000 people reduced to around 500, the security officials said.

Tyre has dwindled from some 175,000 people to only 5,000. Soldiers on Friday dug a mass grave and buried over 70 victims of the bombardment in it, many of them children. Less than two dozen mourners turned up, a sign of how the usually bustling port city has emptied.

The first international Red Cross relief convoy to Tyre arrived Friday after a six-hour journey over damaged roads from Beirut, a spokesman said.

The Lebanese health ministry reported 362 deaths in Lebanon so far in the onslaught, an increase of 55 since it release figures on Thursday. Thirty-four Israelis also have been killed, including 19 soldiers.