A brief truce between Syrian regime forces and rebel groups in three key towns ended early Saturday as the warring parties resumed clashes and shelling, a monitoring group and a mediator said.
Pro-regime forces, including Lebanon's Shiite Hezbollah militia, had agreed on a 48-hour ceasefire, until dawn on Saturday, in the rebel bastion of Zabadani and the government-held villages of Fuaa and Kafraya.
"The ceasefire has collapsed in Zabadani, Fuaa, and Kafraya this morning," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
A Kafraya resident speaking to AFP by phone said "dozens of shells have fallen on the town since early morning." According to Abdel Rahman, "there are clashes and shelling in Zabadani, and opposition fighters are shelling Fuaa and Kafraya." But he had no details on who initially began firing and whether there were any casualties.
Fuaa and Kafraya, the last two regime-held villages in Syria's northwest Idlib province, have been surrounded by a rebel alliance including Al-Qaeda's affiliate Al-Nusra Front.
The siege came in retaliation for a fierce offensive on Zabadani, along Syria's border with Lebanon, by pro-regime forces early last month.
Warring parties were negotiating to reach a broader deal including rebel fighters leaving Zabadani and the evacuation of civilians from Fuaa and Kafraya.
But the talks failed overnight.
The resumption of hostilities was confirmed by Mohammad Abu Qassem, secretary general of Syria's Tadamun (Solidarity) Party and a mediator of the truce.
"The truce has ended, the negotiations have failed, and military operations have resumed in Zabadani, Fuaa, and Kafraya," he told AFP.
This marks the second time a local ceasefire has collapsed for the three towns this month.
The first ceasefire began on August 12 as a 48-hour truce and was extended for another day as negotiators tried but also ultimately failed to reach a broad deal.
The earlier talks also faltered before reaching an agreement on Zabadani's fighters and the fate of civilians in Fuaa and Kafraya, whose residents are minority Shiite Muslims.
The rebels have also sought the release of prisoners held by the regime.
More than 240,000 people have been killed since Syria's conflict began in March 2011, and half of the country's population has been displaced by the war.