Syrian opposition and government forces on Thursday were engaged in hours of fierce battles at and around the Quneitra border crossing, the only crossing between Israel and Syria.

The crossing was captured by the rebels in the early morning, according to a rebel spokesman, who said his organization inflicted “heavy losses” on government troops holding the crossing and were able to destroy four tanks.

But forces loyal to Syrian President Bashar Assad began a counterattack around noon, Al Arabiya reported, leading to a renewed round of fighting. Israel’s Channel 2 said on Thursday afternoon that Assad’s forces had regained control of the area. Syrian state-owned Al-Ikhbariyah TV denied that the rebels controlled the crossing point. It said the Syrian army was pursuing “terrorists” in the Golan.

Some of the fighting was taking place some 200 yards from Israeli territory. An Israeli military source told the Times of Israel that the “situation is still very fluid. Rebels are fighting in both the town [of Quneitra] and the border crossing.”

Israel on Thursday lodged a complaint to the UN over the Syrian military’s use of tanks and armored personnel carriers in the de-militarized zone, a move it said was in violation of the two countries’ ceasefire agreement.

Explosions were heard in the area in the early morning and a mortar shell was reported to have landed at the UN base located at the crossing, injuring at least one person.

An Austrian defense ministry official confirmed to the Associated Press that rebel troops captured the crossing point and that UN forces have withdrawn from the area. The official said that none of the peacekeepers were harmed.

Austria’s contingent with the UN patrols the ceasefire zone between Israeli and Syrian territory on the Golan Heights

The IDF instructed local residents and farmers to avoid the area across from Quneitra. It beefed up its presence along the border and closed nearby roads.

Emergency medical crews on armored ambulances were stationed near Ein Zivan to receive the injured.

The seizure marks the first time since the outbreak of the Syrian civil war in early 2011 that rebel forces have taken over the border crossing with Israel, although at various times they have controlled crossings with Turkey and Jordan.

The Quneitra crossing is chiefly used by UN peacekeepers and is only occasionally utilized for civilian purposes like the transfer of goods, students and brides.

The city of Quneitra was largely destroyed during the 1973 Yom Kippur War and was never rebuilt.

On Wednesday, two mortar shells fell in a field south of the town of Majdal Shams in the Golan Heights. It was not immediately clear whether the mortars exploded in Israeli territory or just across the Syrian border.

Nearby residents reported hearing loud explosions in the area.

There have been previous incidents in the Golan, with gunfire and mortar shells striking the Israel-controlled zone in recent months. Israel believes most of the fire is incidental spillover but in some cases it has said the strikes were deliberate.

In one such incident last month, Syrian troops targeted an Israeli jeep they said had crossed the cease-fire line into the Syria-controlled sector. Syria said it launched two missiles in self-defense, accusing Israel of violating the cease-fire deal.

Over the past day, a series of fierce battles between rebel fighters and forces loyal to Syrian President Bashar Assad have been raging in proximity to the Israeli border.

Syrian State TV on Wednesday reported that Assad’s army was now in full control of the embattled border town of Qusair, where fighting with rebels took place for nearly three weeks.

The report said regime troops “restored security and peace” after successfully dismantling the “terrorist networks” operating in the town over the last few days.

The Associated Press contributed to this report.