Palestinian factions in Syria called for a cease-fire Tuesday after fighting flared at a refugee camp in the capital, Damascus, highlighting a split among Palestinians as the civil war intensifies.

The Yarmouk camp has been the scene of heavy clashes in the past, but the battles subsided last month after Syrian rebels fighting to topple Syrian President Bashar Assad, battled loyalists there to a standstill.

In Tuesday's fighting, five people were killed on Yarmouk Street, four of them when a shell exploded and the fifth in sniper fire, according to The Britain-based Observatory for Human Rights that relies on reports from activists on the ground.

The group said intense clashes were taking place on the edges of the camp, where the Syrian troops are positioned, and the nearby Hajar Aswad district.

In a statement, representatives of 14 Damascus-based Palestinian factions called for a cease-fire and a halt to all military operations to enable medical teams and food supply trucks to enter the camp. They urged gunmen to withdraw from the camp "in order not to bear the responsibility of the continuing displacement of (Yarmouk's) residents."

About half of Yarmouk's 150,000 residents have fled since fighting erupted in mid-December, according to estimates by the United Nations Relief and Works Agency for Palestine Refugees that administers Palestinian camps in the Middle East. Some sought refuge in neighboring Lebanon, and others found shelter in UNRWA schools in Damascus and other Syrian cities.

Dozens have been killed in the fighting, although the United Nations did not provide an exact figure of casualties in Yarmouk violence that has included airstrikes and artillery shelling from the Syrian military and clashes between rebels and Assad loyalists.

Khaled Abdul-Majid, a senior representative of the Palestinian factions that issued the statement, told reporters in Damascus, "We are working to end those clashes."

An UNRWA spokesman told The Associated Press Syrian forces continue blocking the camp's entrances, though residents were allowed to retrieve personal belongings. All UNRWA facilities in the camp remain closed, including three heath centers that are inaccessible because of the fighting, said the spokesman, Sami Mshasha.

When the revolt against Assad's rule began in March 2011, the half-million-strong Palestinian community in Syria stayed on the sidelines. 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 alongside the troops. The PFLP-GC joined the call for a truce on Tuesday. The group is led by Ahmed Jibril, a long-time Assad ally.

Yarmouk is the largest of nine Palestinian camps in Syria. Since the camp's creation in 1957, it has evolved into a densely populated residential district just five miles (eight kilometers) from the center of Damascus. Several generations of Palestinian refugees live there.

Also Tuesday, rebels claimed they shot down a military helicopter at the Taftanaz air base in the northern province of Idlib. The Observatory said the helicopter was flying toward the base.

Rebel units, including the al-Qaida-linked Jabhat al-Nusra group, have battled army troops for weeks for control of the base, from which warplanes have been taking off on missions to bomb rebel-held areas around Syria.

Amateur video posted on YouTube by activists showed black smoke rising from what appears to be an airfield. The video was consistent with AP reporting from the area.

Syria's state-run SANA news agency said army units fought rebels in several areas of Idlib province, including near the Taftanaz base, "killing several terrorists, injuring many others, and destroying their weapons." Troops also battled opposition fighters in the Damascus suburb of Daraya, and in the northern city of Aleppo, the agency said.

In Damascus, Interior Minister Mohammed al-Shaar, who was seriously wounded when a bomb hit his ministry in Damascus last month, attended a Cabinet meeting to discuss Assad's initiative to end the civil war. In a broadcast of Tuesday's meeting on Syrian state TV, al-Shaar was seen with a bandaged right hand and a scar on his forehead.

In a speech Sunday, Assad struck a defiant tone, ignoring international demands to step down and saying he is ready to talk — but only with those "who have not betrayed Syria." He also vowed to continue the battle "as long as there is one terrorist left," a term the government uses for rebels.

The opposition rejected the offer, which also drew harsh international criticism.

The Observatory and other activists also reported heavy fighting Tuesday in suburbs of Damascus, including the Sayda Zeinab district, and shelling of the towns of Beit Saham and Aqraba, both near Damascus airport.

As fighting rages on, more than one million Syrians are suffering from food shortages but are out of reach of vital aid because of the fighting and government restrictions, according a statement Tuesday by the World Food Program.

The conflict started as peaceful protests against the Assad rule, but it turned into a civil war after a harsh government crackdown. More than 60,000 people have been killed since the uprising began in March 2011.