Israel filed a complaint against Syria Monday in the United Nations, alleging that Syrian forces crossed the border between Israel and Syria in the Golan Heights last week.

Israel’s Deputy UN Ambassador, Haim Waxman, sent a letter to the UN Security Council Secretary General, in which he said that during fighting Thursday between the Syrian Army and rebel forces at Jubta al-Hasheb, Syrian forces crossed the 1974 Armistice Line.

Waxman noted that the event is a serious breach of the armistice agreement, which could have far reaching ramifications for security and stability in the region.

Voice of Israel radio reported that the commander of the UN’s peacekeeping force along the Israeli-Syrian border confirmed Israel’s claims and said that Syria had indeed seriously breached the armistice accord. The UN peacekeeping force has requested clarifications from the Syrian regime, he said.