The fresh violence on Tuesday came after the feast of Eid al-Adha came to a close on Monday, with 560 people, including 235 civilians, reported killed during a failed ceasefire attempt over the four-day Muslim holiday.
"Clashes broke out overnight in Al-Hajar Al-Aswad district between rebels and the army, spreading into the adjacent Yarmuk Palestinian camp. The Popular Front for the Liberation of Palestine-General Command joined on the side of the army," said Rami Abdel Rahman, director of the Syrian Observatory for Human Rights watchdog.
"Every time the fighting spills into Yarmuk, the General Command gets involved," said Abdel Rahman.
The Syrian Revolution General Council, a network of activists on the ground, also reported that heavy fighting erupted between the Free Syrian Army and members of the PFLP-General Command in Yarmuk.
The Yarmuk district is home to more than 112,000 Palestinians, who are divided over the 19-month revolt that has left 35,000 dead in the country.
In early August, Palestinian president Mahmud Abbas condemned shelling on the camp, which killed 21 civilians, and also chided the PFLP-General Command for its role in dragging Palestinians into the bloody conflict.
Elsewhere in Syria on Monday, the military renewed shelling attacks on the northern city and province of Aleppo, the central city of Homs, the southern province of Daraa and the northwest province of Idlib, the Observatory said.
Regime warplanes made two air strikes on the Idlib town of Maaret al-Numan, where fighting has raged since the rebels overran the town on October 9 cutting off a key army supply route along the Aleppo-Damascus highway.
Fierce clashes south of the town on Monday left two soldiers killed, while battles erupted around the nearby Wadi Daif army camp between troops and rebels, including fighters from the jihadist Al-Nusra Front, the Observatory said.
Regime helicopters meanwhile dropped three barrel bombs on the nearby village of Maarshmareen, which also came under artillery fire from troops stationed nearby.
In Doha, Qatari Prime Minister Sheikh Hamad bin Jassem al-Thani has accused the Syrian regime, with the complicity of the international community, of waging a "war of extermination" against its people.
Sheikh Hamad in an interview with Al-Jazeera satellite channel late on Monday took issue with UN-Arab League peace envoy Lakhdar Brahimi, who earlier in the day had characterised the deadly conflict ravaging Syria as a "civil war".
"What is happening in Syria is not a civil war but a war of extermination against the Syrian people," Sheikh Hamad said.
This war, he charged, was being waged "with a licence to kill, endorsed firstly by the Syrian government and secondly by the international community".
He was apparently referring to Russia and China, which have repeatedly vetoed UN security council resolutions threatening action against President Bashar al-Assad's regime.
"We have confidence in Mr Brahimi ... but we need him to develop a clear proposal for a solution that can be put before the security council paving the way for a transition period and a transfer of power," said Sheikh Hamad.
Brahimi, who saw the truce he had brokered for the four-day Muslim Eid al-Adha holiday shattered in an explosion of violence soon after it took effect on Friday, said in Moscow the situation in Syria was "bad and getting worse."
"If it's not a civil war, I don't know what it is," he said after talks with Russian Foreign Minister Sergei Lavrov.
Brahimi, who is also due to visit China, is to go to the UN security council in November with new proposals to push for talks between Assad and the opposition.
Qatar is widely accused of arming rebels fighting Assad's forces.
It called, without success, in the UN general assembly last month for an Arab intervention force in Syria and a no-fly zone to protect refugees.
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