UN still negotiating release of peacekeepers

"The mission has been in touch with the peacekeepers by telephone and confirmed they have not been harmed," UN spokesman Martin Nesirky told reporters.

"The United Nations is working to secure the release of the peacekeepers."

A UN official, speaking on condition of anonymity, said the UN Disengagement Observer Force (UNDOF) mission was "negotiating with the armed group and the Syrian authorities" to obtain a release.

The force has cut down the number of patrols in the ceasefire zone because of the abductions and may further review its security, the official said. "We will have to adjust," the official added.

UN peacekeeping chief Herve Ladsous is to brief the UN Security Council on the abduction on Friday.

The 21 Filipino troops were abducted on Wednesday by rebels who had at first demanded that Syrian government forces pull back from a village in the Golan zone.

The soldiers were "lightly armed" for self defense, according to the UN peacekeeping department.

UNDOF has been in the Golan Heights since 1974 monitoring a ceasefire between Syria and Israel. In recent months the Syrian civil war has spilled over into the zone.

Five Austrian troops in the force were wounded when they became caught in crossfire in a convoy taking them to Damascus airport in November.

"Since then we have had a flurry of carjackings, intimidations, threats at gunpoint," the official said.

Opposition rebels have crept into villages into the ceasefire zone and set up some bases, according to the official.