The United Nations has condemned the bloody clashes in northwest Syria that have left entire families dead. Clashes between security forces and Assad supporters have led to the highest death toll since the 2011 revolution.

UN Human Rights Commissioner Volker Turk has called for an investigation into the killings and for those responsible to be held accountable. "We are receiving disturbing reports of the killings of families, including women, children, and surrendered fighters. "The killings of civilians must stop immediately," he said.

The clashes began on Thursday when pro-Assad fighters ambushed security forces in the town of Jableh in Latakia province. The violence has since spread, with civilians, including members of the Alawite minority, also being targeted.

The Britain-based Syrian Observatory for Human Rights (SOHR) said more than 1,000 people had been killed, including 745 civilians, 125 security personnel, and 148 Assad supporters.

However, the death toll varies. The Syrian Network for Human Rights (SNHR) said Assad's supporters had killed 148 civilians, while security forces had killed 327 civilians and captured fighters.

On Sunday, Syria's interim president, Ahmed al-Shara, said the situation aligned with "the challenges ahead" and called for national unity.

"We must preserve our national unity and internal peace. We can live together," he said.

The Syrian president then announced the formation of a seven-member commission, including judges and a lawyer. The commission's goal is to investigate the killings of civilians and security forces, and its report must be submitted within 30 days.

Meanwhile, the United States and Russia have appealed to the UN Security Council, proposing to convene a closed-door meeting on Monday to discuss the escalation of violence in Syria.