Syrian rebels and forces loyal to President Bashar Assad battled for control of the Quneitra border crossing to Israel on Thursday,  as heavy clashes raged between the opposition and the presiden's forces, the Israel Defense Forces confirmed.

The rebels opened their offensive on Quneitra early in the morning and seized it shortly after. IDF soldiers positioned in lookout towers around noon said Assad's forces had regained control of the crossing, amidst heavy fighting.

The rarely used crossing, in a UN-patrolled demilitarized zone on the Golan Heights, is the only transit point between Syrian and Israeli disengagement lines set in 1974. The Britain-based Syrian Observatory for Human Rights said this was the first time that rebels had seized the crossing. 

Eyewitnesses in Quneitra reported heavy exchange of fire and smoke rising from the area. The crossing on the Syrian side of the border was badly damaged, they said.

Quneitra is less important than other border crossings, a source in the Syrian opposition told Haaretz. "The crossing may have symbolic [significance], but it doesn't have a strategic value because it does not function as a line for logistical support," he said.

The United Nations' peacekeeping operations chief confirmed on Thursday there had been incidents including shooting on the Syrian-Israeli border. "Yes there was shooting," Herve Ladsous told reporters during a visit to Paris.

"We are following events in the Golan Heights, which is a very sensitive region, with particularly close attention," he added, while not confirming that the crossing had been captured.

Ladsous said the 1,000-strong United Nations Disengagement Observer Force (UNDOF) had taken measures to ensure the safety of its personnel but stressed that its involvement was not called into doubt by the incidents.

Ladsous said the region had been "extremely confrontational" in the past year.

"We are doing everything we can to reduce risks. We have closed posts that were too exposed, reinforced our equipment and vehicles, and our activities are more static," he said.

Israel is worried that the Golan, which it captured from Syria in 1967, will become a springboard for attacks on Israelis by jihadi fighters, who are taking part in the armed struggle against Assad.

Israel's defense establishment also sees the capture of Quneitra as key to the fighting due to its strategic location on the road leading from south Syria to Damascus.  Assad had already lost control over Syria's border crossings, mainly those with Iraq and Turkey. In the Golan Heights, the buffer zone between Syria and Israel - excluding Quneitra - has already been taken under the control of rebel groups.

Two shells fired during the clashes landed inside the Israeli-held territory early Thursday, causing no casualties or damage. An IDF spokeswoman said the area leading to Quneitra had been closed off, but gave no other details on the fighting

Alex Shalom, an Israeli farmer from the Golan Heights, said he saw heavy smoke rising from the crossing and the IDF evacuating people from the site.

Two Syrians who were wounded in the fighting had been taken into Israel for treatment, one with gunshot wounds to the chest and the other to the stomach, and IDF spokeswoman said. She could not say whether they were rebels or army soldiers.

Both of the wounded Syrians were taken to the Sieff Medical Center in Safed for treatment and surgery.  A live fragmentation grenade was found in the pocket of one of the wounded Syrians. Sappers were called in to safely detonate the explosive. Medical staff were told to remain at a distance from the trauma ward. 

Meanwhile in the area of Qusair, Syrian troops and Hezbollah fighters were pushing toward nearby villages a day after seizing control of the key town on the Lebanese border.

Insurgents seeking to overthrow Assad were putting up a fierce fight around the villages of Debaa and Buwayda as their opponents attacked rebel-held territory, activists and a photographer in the area said. The villages were enduring heavy artillery fire, according to the Syrian Observatory for Human Rights.

Also Thursday, a Turkish soldier was wounded in a clash with gunmen in a group of about 500 people trying tocross into Turkey from Syria, the Turkish military said onThursday.

It said troops in Hatay province fired across the border on Wednesday after coming under fire themselves from the gunmen who had believed the soldiers would prevent the party from crossing.

The Turkish soldier, wounded in the knee, was the first such casualty in several similar border incidents in the past week.