BEIRUT/PARIS: Heavy fighting gripped a flashpoint region near the Syrian capital Sunday, leaving seven civilians dead and threatening a nationwide truce designed to pave the way toward peace talks.

Further east, Syrian government troops lost ground to a brutal assault by Daesh (ISIS) near the key Deir al-Zor military airport.

The violence in the water-rich Barada Valley, which has raged since Dec. 22, has tested the country’s fragile cease-fire and restricted the flow of water to the capital. Despite an agreement to allow maintenance workers in to fix the water facility in the rebel-controlled valley, the violence continued, also trapping an estimated 100,000 residents.

Sunday, shells fell on Al-Reem banquet hall in Deir Qanoun village in the valley that houses hundreds of civilians who had escaped the intensified fighting. The activist-operated Wadi Barada Media Center said 12 were killed and more than 20 were injured. The group posted pictures of the bloodied floors of the hall, some of them showing bodies with severed limbs.

Fouad Abu Hattab, an exiled resident of Barada Valley and an activist with the group, said medical teams have been unable to move around the valley because of the fighting and it is not clear if the dozens of injured are getting any immediate care.

The Syrian Civil Defense, a team of volunteer first responders in the rebel-held parts of Syria, also put the death toll at 12, saying the shelling hit a displaced people’s center.

The Lebanese Hezbollah group, which has fighters on the side of the Syrian government, said pro-government troops seized a hill overlooking the water source in the valley Sunday.

Local officials struck a truce with Syrian authorities Friday to allow maintenance teams into Wadi Barada to restore water to Damascus, but the deal was called off after chief negotiator Ahmed al-Ghadban was killed the next day.

The two sides accused each other of assassinating the retired army officer, who had only assumed his duties to restore the water supply Saturday.

“The agreement was considered null this morning after the regime’s multiple violations and especially after the killing of the negotiations official,” Shami said.

Shami told AFP the government’s maintenance workers left Wadi Barada without completing the repairs, leaving 5.5 million in Damascus and its suburbs without water.

An official from Syria’s Reconciliation Ministry earlier told AFP the local deal in Wadi Barada “had not completely collapsed.”

“We are communicating and pursuing new efforts in parallel with the ongoing military action,” the official said.

Meanwhile, in eastern Syria, Daesh militants kept up their offensive on government-held areas of the contested city of Deir al-Zor, attacking a military air base from several fronts. The group said on social media it attacked the airport from the west Sunday, seizing a sentry base used by government soldiers there.

The Syrian Observatory for Human Rights said the militants also advanced on a hill overlooking the city. If it secures the hill, the Observatory said, Daesh militants would be able to sever the road between the air base and another army base nearby.

Deir al-Zor carries strategic significance for Daesh as it links the group’s Iraq territory to its de facto capital of Raqqa in Syria. The group is under intense pressure in both countries and has lost significant territory.

The extremist group, which controls most of Deir al-Zor province, has kept the provincial capital under siege since 2014. The new multi-pronged assault that began Saturday is its most intense attack on government areas since January 2016.Government forces have withstood the encirclement thanks to air-dropped humanitarian assistance, weapons and ammunition flown into the airport. Remaining residents have reported malnourishment and starvation amid severe shortages of food, water and fuel.

The fresh advance came “despite more than 120 airstrikes carried out by regime forces on militants positions since Saturday morning, in addition to heavy artillery fire,” said Observatory head Rami Abdel-Rahman.

Daesh unleashed a wave of tunnel bombs and suicide attackers against government forces Saturday, leaving 12 government fighters dead.

Although they support opposing sides in Syria’s war, Moscow and Ankara have worked closely to negotiate the nationwide truce and to prepare talks in the Kazakh capital Astana on Jan. 23.

U.S. President-elect Donald Trump’s transition team has been invited to take part in the talks, but has not yet officially responded.

Secretary of State John Kerry Sunday urged the incoming administration to accept an invitation from Russia to attend the talks next week.

Attendance by the new president’s team would be a strong signal of Trump’s determination to improve relations with Russia.