United Nations, Dec 20 : UN Secretary-General Antonio Guterres has urged Israel to stop violations of Syria's sovereignty and territorial integrity.

Speaking at a press conference on Thursday, Guterres condemned Israel's extensive airstrikes on Syria aimed at destroying strategic weapons and military infrastructure and its troops' entry into a demilitarised zone between Syria and the Israeli-occupied Golan Heights.

"They are violations of Syria's sovereignty and territorial integrity and they must stop," he said.

"Let me be clear: There should be no military forces in the area of separation other than UN peacekeepers. And those peacekeepers must have freedom of movement to undertake their important work."

Guterres underscored that Israel and Syria must uphold the terms of the 1974 Disengagement of Forces Agreement, which remains fully in force.

"This is a decisive moment -- a moment of hope and history, but also one of great uncertainty," the UN Chief told reporters.

"Some will try to exploit the situation for their own narrow ends. But it is the obligation of the international community to stand with the people of Syria who have suffered so much," he said.

Since a lightning rebel offensive ousted Syrian President Bashar al-Assad earlier this month, Israel has carried out hundreds of airstrikes that it says are aimed at destroying strategic weapons and military infrastructure.

Israeli troops also moved into a demilitarised zone between Syria and the Israeli-occupied Golan Heights - created after the 1973 Arab-Israeli war -- that is patrolled by UN peacekeepers.

Israeli officials have described the move as a limited and temporary measure to ensure the security of Israel's borders but have given no indication of when the troops might be withdrawn.

The International Commission on Missing Persons in The Hague has said it had received data indicating there may be as many as 66, as yet unverified, mass grave sites in Syria. More than 150,000 people are considered missing, according to international and Syrian organisations, including the United Nations and the Syrian Network for Human Rights, it said.

A violent crackdown by Assad on peaceful pro-democracy protesters in 2011 led to a civil war. Millions of people fled Syria with millions more internally displaced.

/IANS