Majdal Shams, Golan Heights (CNN) -- Rebels aided by al Qaeda-linked militants seized control of the only border crossing between Syria and the Israeli-occupied Golan Heights on Wednesday.
The capture of the Quneitra crossing by Syrian rebels, including members of the al Qaeda-linked al-Nusra Front, represents a new dynamic in a war long feared not only for its deadly effects inside Syria but for threatening to widen into a destabilizing regional conflict.
The border crossing made headlines earlier this week, when American journalist Peter Theo Curtis was handed over on the Syrian side of the checkpoint by the al-Nusra Front to U.N. peacekeepers.
During the fighting on Wednesday between Syrian forces and rebels, three errant mortar rounds and some small-arms fire crossed into Israeli-controlled territory, IDF spokesman Lt. Col. Peter Lerner said.
An Israeli military officer was moderately injured, the IDF said on Twitter, and Israeli forces responded by striking two Syrian military positions.
The Israeli military has closed the area around the border crossing.
An activist in the Golan Heights, Shamil al-Jolani, said the Islamist group Ahrar al-Sham al-Islamiya and other rebel groups, not all of them Islamist, also were involved in the fighting.
Video from the scene showed heavy smoke rising from the Syrian side of the crossing. A journalist working with CNN said that heavy shelling and gunfire erupted earlier from the Syrian side but that the situation had since calmed.
Jolani said some fighters were able to reach the crossing despite bombardment by Syrian warplanes. Because of agreements with Israel, Syrian forces could not bomb the forces at the crossing, he said.
Wednesday's fighting marks at least the second time rebels have attacked the crossing.
In June 2013, rebels and Syrian forces battled for control of Quneitra. The violence prompted Austrian troops to pull out of a United Nations peacekeeping force in the Golan Heights. Israel sent tanks and troops to the border for a time, as well.
Israel seized control of the Golan Heights during the 1967 Six-Day War, and fought off an attempt by Syria in 1973 to retake the rocky plateau.
In 1981, Israel annexed the Golan Heights. It is considered to be occupied territory by the international community.
Ben Wedeman reported from the Golan Heights, and Michael Pearson and Chelsea J.Carter reported and wrote from Atlanta. CNN's Samira Said and Hamdi Alkhshali also contributed to this report.