Fighting is continuing between Lebanese troops and Islamist militants at the Nahr al-Bared camp for Palestinian refugees near the northern city of Tripoli.
Dozens of people - soldiers, militants and civilians - have been killed in the violence, which began on Sunday.
Lebanese troops are exchanging fire with militants belonging to Fatah al-Islam, a radical group suspected of links to al-Qaeda, who are holed up in the camp.
A UN convoy tried to deliver aid to the camp, where conditions are said to be deteriorating, but was forced to leave after shells exploded near its vehicles.
A few people have been evacuated from Nahr al-Bared, but the camp houses more than 30,000 people, many of whom remain trapped inside.
Officials fear the fighting could trigger broader unrest. There have been angry protests at other Palestinian refugee camps in Lebanon and two blasts in Beirut.