Syrian government troops have battled rebels for control of a Christian village in western Syria for the second consecutive day, anti-government activists say.

They said that clashes raged on the outskirts of Maaloula on Thursday, a day after rebels entered the ancient village.

Amateur video footage uploaded on Wednesday showed rebel fighters engaged in fierce gunfights in the village, which is on a UNESCO list for consideration to become a world heritage site.

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The Britain-based Observatory for Human Rights (SOHR) said the rebel forces included members of the of al-Qaeda-affiliated Jabhat al-Nusra group.

Despite a heavy army presence in the village, the SOHR said the rebels patrolled its streets on foot and in vehicles, briefly surrounding a church and a mosque before leaving early on Thursday.

Activists said fighters had withdrawn from the centre of the town after army reinforcements arrived.

The rebels launched the assault on the village, about 60km from Damascus, on Wednesday after al-Nusra detonated a bomb at a government-operated checkpoint at the entrance to the mountain village.

The village is home to 3,300 residents, some of whom still speak a version of Aramaic, the ancient language of Biblical times believed to have been spoken by Jesus.

Meanwhile, heavy clashes between President Bashar al-Assad's troops and al-Nusra fighters also persisted in the mountains near Damascus on Thursday, according to the Observatory, which collects information from a network of sources on the ground.

Scientific centre attacked

The Observatory and state news agency SANA also reported that two explosions went off near a scientific research centre in Soumariya area, in western Damascus, on Thursday.

SANA reported that four people were killed and six others injured in what it said was a car bomb attack.

SANA said the blast damaged shops and cars near the centre.The centre, established in 1965, tests industrial products, its website said.

The Syrian conflict started in March 2011 as largely peaceful protests against Assad's rule, but has since turned into a bloody civil war that has claimed more than 100,000 lives, according to a UN tally.

After two years of fighting, the civil war has hit a stalemate, with the rebels controlling much of the countryside in the north, east and south, and the regime holding on to most urban centres in the west, where the majority of Syrians live.

Source: Al Jazeera and agencies