Syrian government forces are keeping up their pressure on the country's strategic southwest, using artillery, airstrikes and dropping barrel bombs that target rebel-held parts of the region, activists said.
The Britain-based Syrian Observatory for Human Rights said more than 12 barrel bombs hit the province of Daraa, the first use of the rudimentary and non-discriminatory weapons there in over a year.
Rockets and artillery shells have also targeted northern and eastern Daraa, and there were reports of overnight airstrikes on Busr al-Harir, a northeast Daraa town where government troops are trying to isolate the rebels.
Rebel factions, meanwhile, said they responded with missiles at a government air base in the adjacent Sweida province.
The Observatory said 16 people have been killed in government strikes since Tuesday, including nine children. At least 12,000 people have been displaced by the fighting.
The government campaign in the southwestern Syrian region bordering Jordan and the Israeli-occupied Golan Heights comes despite U.S. warnings of "serious repercussions" for anyone violating a de-escalation agreement in place since last July.
The truce, referred to as a de-escalation zone, was negotiated between Russia, the Syrian government's main ally, Washington and Jordan and has kept the area calm.
But the truce began to unravel in recent weeks as the Russia- and Iran-backed Syrian government turned its attention southward, after seizing opposition-held areas near the capital, Damascus. Israel, meanwhile, has grown more active in protesting Iran's expansion in Syria, carrying out airstrikes against suspected Iranian targets in the area.
US State Department spokeswoman Heather Nauert said yesterday that Washington was "deeply troubled" by the Syrian government operations in the area and called on Moscow to "restrain" its ally from further actions that risk broadening the conflict.
The region is a mix of government and rebel-controlled areas, with rebels controlling parts of Daraa city and areas along the border.