The United States intervened directly in the crisis in Lebanon for the first time today, flying six military aircraft carrying ammunition into Beirut to help the country's Army battle against Islamic extremists holed up in a Palestinian refugee camp.

The White House confirmed that the Arab-owned planes, carrying weapons and ammunition from US army bases and depots all around the Middle East, had landed at Beirut International Airport.

The US military's intervention comes after a direct appeal to the Bush Government by Fouad Siniora, the Lebanese Prime Minister, whose Army is struggling to defeat the Fatah al-Islam group which has taken over the Nahr el-Bared camp, near the Lebanese city of Tripoli.

“The United States has existing agreements to provide (military) assistance to Lebanon. Under those agreements we are expediting the delivery of supplies,” Gordon Johndroe, a spokesman for the White House National Security Council, told the Reuters news agency today.

The fighting in the camp has caused a humanitarian crisis, with all but 15,000 of Nahr el-Bared's 40,000 residents forced to flee to a neighbouring camp and with an unknown number having been killed in the midst of running battles between the Army - which is surrounding Nahr el-Bared - and the extremists.

At least 33 Lebanese soldiers and 25 militants from Fatah al-Islam are believed to have died in the fighting, in what has been described as Lebanon's worst violence since the 1975-1990 civil war.

UNRWA, the UN agency which cares for Palestinian refugees, today said that it was still unable to enter the camp to provide desperately-needed supplies to its remaining civilians.

Hoda Elturk, a spokeswoman for UNRWA, said: "The humanitarian situation in Nahr al-Bared is deteriorating. We have our trucks full of food and water ready. It’s not secure enough for our staff to enter."

As Palestinians fled from the fighting at Nahr el-Bared, there were reports today of mass overcrowding at the nearby Badawi refugee camp, on the northern outskirts of Tripoli, as refugees poured in.

The narrow winding streets of the camp were reported to be overflowing with a heaving throng of people, and facilities were stretched to the limit.

Residents of Badawi have thrown open their homes to the newcomers and the overflow are staying in schools and any open space in the camp. Aid agencies have been distributing foam mattresses but there are not enough to go around.

“The scale of this disaster is more than Badawi can cope with,” said Sheikh Walid Abu Hait, a Sunni cleric from Nahr al-Bared.

“People are sleeping on the ground, the young, the old and the sick with no blankets or sheets.”

Virginia de la Guardia, the spokeswoman for the International Committee of the Red Cross, which has been coordinating the relief effort at Badawi, said that 20 tonnes of food had been provided for the camp and another 200 tonnes was en route from Jordan. “The situation really is very serious,” she said.

Although a fragile ceasefire seemed to be holding around Nahr el-Bared so far today, there were reports of renewed gunfire between Lebanese troops and Fatah al-Islam late last night as the Army continued to mass on the outskirts of the camp in preparation for an apparent ground assault.

If a full-scale raid is launched, it would be the first time any Lebanese military forces have entered the camp since 1969, when an agreement was struck banning their entry.

Lebanese military leaders have complained that their 40,000-strong Army is already stretched to the limit. It has deployments along the border with Israel in southern Lebanon - a conflict-zone which saw a fully-blown war between Israel and the Iranian-backed Hezbollah militia last summer.

Further troops are positioned along the Syrian border in the north and east, and in and around Beirut where Hezbollah earlier this year demonstrated for the Government's resignation.

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