BEIRUT (Reuters) - A 48-hour ceasefire was declared on Wednesday to halt fighting between Syrian insurgents and the army and its Lebanese militant Hezbollah ally in the rebel-held town of Zabadani and two Shi'ite Muslim villages in Idlib province.

The United Nations envoy for Syria said last month that government air strikes had caused widespread death and destruction in Zabadani, and expressed concern that civilians were trapped both there and in al-Foua and Kefraya villages.

Sources on both sides of the civil war told Reuters earlier on Wednesday the truce was to begin at 6 a.m. (11 p.m. EDT), and negotiations would continue. The rebel group Ahrar al-Sham had led the negotiations on the insurgents' side.

"A ceasefire began at 6 a.m. today for 48 hours to halt military operations in Zabadani," Hezbollah's al-Manar reported. "It also includes the two villages of al-Foua and Kefrayain the Idlib countryside."

The Syrian Observatory for Human Rights, a Britain-based group that reports on the war, said no fighting had been reported in Zabadani, Kefraya or al-Foua after the ceasefire's agreed start time. "So far there is calm," Rami Abdulrahman, who runs the Observatory, told Reuters.

Hezbollah, an Iranian-backed Shi'ite group with a powerful militia, has been a crucial ally of President Bashar al-Assad in the four-year-old Syrian conflict.

Zabadani, about 45 km (30 miles) northwest of the capital Damascus and about 10 km from the border with Lebanon, has been the focus of a weeks-long offensive by the armyand Hezbollah aimed at wresting control of the town from rebels.

The two Shi'ite villages have been targeted by an insurgent alliance that includes both the Sunni Islamist Ahrar al-Sham and the al Qaeda-linked Nusra Front.

The Observatory said talks would continue on evacuating fighters from Zabadani and sending food aid to Kefraya and al-Foua where thousands of people are under rebel siege.

A source close to the negotiations from the insurgents' side earlier told Reuters: "The ceasefire has been agreed on but there are other points and negotiations are continuing on them."

A source close to Damascus who is familiar with ceasefire agreement said the talks were being held through an intermediary. "The ceasefire will begin and some (people) who are in critical condition will be evacuated. Talks will discuss further steps," the source said.

Ahrar al Sham said last week that it was holding talks with an Iranian delegation overZabadani.

Ahrar al Sham said at that time those talks were halted due to the Iranian delegation's "determination to empty Zabadani of civilians and fighters and displace them to another areas".

It said some fighters were refusing to leave Zabadani.

The Observatory said negotiations were held between Ahrar al Sham and Iranian delegations and Hezbollah, but the source who is close to Damascus said the agreement was made between the insurgent group and the Syrian government.

Hezbollah's military role inside Syria has been growing steadily since the start of the conflict in 2011. The Syrian government has described the group as its main ally in the fight against the insurgents battling to topple Assad.