The United Nations said it has sent a team to resolve the situation, while the 15-member Security Council condemned the incident and demanded the immediate release of the peacekeepers.

UN peacekeeping chief Herve Ladsous told the council in an emergency briefing that the fighters who had detained the peacekeepers were "associated with Syrian armed opposition group elements," said Russian UN Ambassador Vitaly Churkin, who is president of the council in March.

He added that the captors have made "some demands associated with the actual situation on the ground in Syria." He gave no further detail.

Videos purporting to show Syrian rebels with the seized convoy were posted to YouTube on Wednesday. Syria's two-year civil war, which has killed more than 70,000 people, has been spilling into the Golan Heights area.

"The UN observers were on a regular supply mission and were stopped near Observation Post 58, which had sustained damage and was evacuated this past weekend following heavy combat in close proximity, at Al Jamlah," the United Nations said in a statement issued in New York.

Israel captured the Golan Heights from Syria in a 1967 war. Syrian troops are not allowed in the area of separation under a 1973 ceasefire formalized in 1974. Israel and Syria are still technically at war. The area is patrolled by UN peacekeepers.

Israel warned the UN Security Council on Monday that it could not be expected to "stand idle" as Syria's civil war spills over its border, while Russia's Churkin accused armed groups of undermining security between the states by fighting in the Golan Heights.