The United Nations on Monday was forced to pull back hundreds of peacekeepers to the Israeli-side of the Golan after Syrian rebels advanced on their positions.
Syrian Ambassador Bashar Jaafari said fighters from Jabhat al-Nusra "had succeeded in occupying all of the Syrian side" of the Golan, driving out the troops from the UN Disengagement Observer Force (UNDOF).
"The terrorists are now using United Nations cars, which hold the emblem of the United Nations forces in the Golan. They are using the uniform of the UNDOF, the weapons of UNDOF, the positions of UNDOR to shell on the Syrian army as well as on the civilians in villages," Jaafari told reporters.
The UN Security Council is due to discuss the crisis on the Golan during a session on Wednesday after more than 40 Fijian UNDOF troops were held hostage for two weeks by Al-Nusra.
Jaafari accused Israel, Qatar and Jordan of being behind a "very big plot" to destabilize Syria by letting the Syrian rebels take control of part of the buffer to set up a "safe zone" from where it can wage attacks.
UNDOF monitors a 1974 ceasefire between Israel and Syria on the Golan Heights.
Some 510 square kilometers of the Golan remain on the Syrian side of the ceasefire line, with UNDOF overseeing a buffer zone stretching some 70 kilometers from Lebanon in the north to Jordan in the south.
Six countries contribute troops to the 1,200-strong UN force on the Golan: Fiji, India, Ireland, Nepal, the Netherlands and the Philippines.