BEIRUT (AP) -- Syrian fighter jets bombed a Palestinian refugee camp in Damascus Tuesday for the second time this week after rebels made significant advances, seizing large areas within the camp, activists said.
Meanwhile, American foreign correspondent Richard Engel of NBC said that he and his crew escaped unharmed during a firefight after being held captive for five days by pro-regime gunmen.
The rebels fighting to topple Assad's regime have pressed hard against the regime in the past weeks, capturing air bases and military installations in and around Damascus.
Their offensive in the Palestinian refugee camp of Yarmouk in southern Damascus, which began Friday, is aimed at driving out a pro-government Palestinian faction.
The British-based Syrian Observatory for Human Rights and other activists in the camp said fighter jets dropped bombs on the camp Tuesday afternoon, but there was no immediate word of casualties.
Similar airstrikes on Sunday killed at least eight people in Yarmouk.
When the revolt against Assad's rule began 21 months ago, the half-million-strong Palestinian community in Syria stayed on the sidelines.
But as the civil war deepened, most Palestinians backed the rebels, while some groups -- such as the Popular Front for the Liberation of Palestine-General Command -- have been fighting on the government side.
By Tuesday afternoon, the Syrian military deployed several tanks along camp's main entrance, residents said. There were no Syrian government troops in the camp and most of the fighting was between rebels and PFLP-GC gunmen, they said. The group is led by Ahmed Jibril, Assad's longtime ally.
Activist videos posted online show armed men moving through the streets of the Damascus camp, as people cheer their presence and chant "God is great." Gunfire is heard in the background, and the narrator says the rebels are members of the Free Syrian Army.
Rami Abdul-Rahman, chief of the Observatory, said rebels were now in control of most of the camp but intense clashes were continuing in several areas.
The fighting in the camp has forced an exodus of Palestinian refugees and Syrians who came to the camp in past weeks to escape violence elsewhere in the city, according to United Nations officials.
Civilians continue to leave Yarmouk, with some heading to UNRWA installations around Damascus. Others are fleeing to other Syrian cities and many are headed to the Lebanon-Syrian border, said Sami Mshasha, spokesman for the U.N. Relief and Works Agency.
In Geneva, the United Nations said 4 million people need humanitarian aid in Syria.
World Food Program spokeswoman Elisabeth Byrs told reporters Tuesday that about 2.5 million Syrians need food aid, but her agency can only reach 1.5 million of them.
The World Health Organization said the Damascus Hospital, the largest hospital in the capital, is now receiving 70 to 100 patients a day whose most frequently observed injuries are burns, gunshots and injuries from explosions resulting from the escalating violence.
WHO spokesman Tarik Jasarevic said women and children are increasingly among the injured and said the hospital has had an increase in cases of severe malnutrition from rural Damascus and other Syrian provinces.
The 21-month battle to bring down the Assad regime has forced some 3 million Syrians from their homes, according to a new estimate. Cold, wet winter weather is making life increasingly difficult for the displaced. Among those who left their homes are more than 500,000 who fled to neighboring countries -- Turkey, Lebanon and Jordan.
As the violence escalates, the Syrian regime's few remaining allies appear to be preparing for the possibility of Assad's fall.
Russia said on Tuesday it was sending warships to the Mediterranean amid official talk about a possible evacuation of its citizens from Syria.
Moscow has been President Bashar Assad's main ally, shielding him from international sanctions over a brutal crackdown on an uprising that began in March 2011 and turned into civil war.
Last week, however, a senior Russian diplomat said for the first time that Assad is losing control and the rebels might win the civil war, a statement that appeared to signal that Moscow has started positioning itself for an endgame in Syria. But the Foreign Ministry disavowed Mikhail Bogdanov's statement the next day, saying his words were misinterpreted and that Moscow's position on the crisis hasn't shifted.
The Russian Defense Ministry did not say whether the navy ships that set off for the Mediterranean are intended for an evacuation of Russian citizens. It said the ships will rotate with those that have been in the area since November.