Heavy clashes between Syrian army forces and rebels aiming to topple President Bashar Assad’s regime flared up in the Syrian Golan Heights Monday, as the two sides continued to wage battle for control of the strategic Quneitra crossing along Israel’s northeastern border.

The Syrian army was reported to have shelled the area with massive artillery fire, and at least one heavily armed tank was said to have been taking part in the fighting as well, Reuters reported.

Israel Radio reported that at least one mortar fired from Syria landed in Israel.

An Army Radio reporter in the area wrote on Twitter that some fire was straying onto the Israeli side of the border.

An IDF spokesman announced that areas near the border would be closed to civilians. However, the Golan Regional Council said that no special instructions had been given to them.

The Britain-based Syrian Observatory for Human Rights says the fighting on Monday was focused around the town of Hamidiyeh in Quneitra province.

The Observatory says there were casualties on both side, but did not have exact figures.

On Sunday night, a mortar shell fired from Syria landed on the Israeli side of the Golan Heights, followed by bursts of gunfire aimed at reporters and UN peacekeepers. There were no reports of injuries.

Over the past few days, Syrian troops have fought fiercely to regain control of Quneitra, the only border crossing between Israel and Syria, after it had been seized by rebel groups, including the al-Qaeda-affiliated Nusra Front, last week.

The clashes between Syrian forces and the Nusra Front have caught United Nations peacekeepers in the crossfire, and 44 UNDOF peacekeepers, from Fiji, remained in Nusra captivity, after they had been kidnapped Thursday.

Philippine military chief Gen. Gregorio Pio Catapang shows reporters where Filipino peacekeepers in Golan Heights have been repositioned during a press conference at Camp Aguinaldo military headquarters in suburban Quezon city, Philippines on Sunday Aug. 31, 2014. (photo credit: AP Photo/Aaron Favila)

Philippine military chief Gen. Gregorio Pio Catapang shows reporters where Filipino peacekeepers in Golan Heights have been repositioned during a press conference at Camp Aguinaldo military headquarters in suburban Quezon city, Philippines on Sunday Aug. 31, 2014. (photo credit: AP Photo/Aaron Favila)

The peacekeepers became trapped after Syrian rebels entered the UN-patrolled buffer zone between Syria and Israel this past week, seizing the Fijian soldiers and demanding that their Filipino colleagues surrender. The Filipinos, occupying two UN encampments, refused and clashed with the rebels on Saturday. On Sunday morning, 40 Filipino peacekeepers who were surrounded by rebel forces made a bold escape from the border under fire, joining 75 others who had previously managed to escape.

The Fijian military said Sunday that it was pursuing negotiations with the Syrian Islamic rebel group in an attempt to free the 44 troops, but still had not received word on where the soldiers were being held.

Fiji has been told that the men were unharmed and were being treated well, but “we still at this stage cannot confirm the exact location of our troops. We are continuing negotiations at all levels,” said Brig. Gen. Mosese Tikoitoga, head of the Fijian army, according to a Reuters report.

A UN peacekeeper on an armored personnel carrier (APC) along the Israel-Syrian border on August 30, 2014 (photo credit: Flash90)

A UN peacekeeper on an armored personnel carrier (APC) along the Israel-Syrian border on August 30, 2014 (photo credit: Flash90)

Also Sunday, Israeli forces shot down an unmanned aircraft as it entered the country from Syria, near the Quneitra crossing. The drone was hit with a Patriot missile as it flew above the border.

Defense Minister Moshe Ya’alon praised the army’s swift response, which he said was “admirable,” and warned that Israel would not tolerate any attacks on its troops, “whether intentional or unintentional.”

“These past few weeks have proven that our tolerance for attempts to harm us is low, and if someone tries to test us, we will respond aggressively,” he said in a statement, alluding to the war in Gaza.

It was not clear who had launched the drone.

Al-Nusra Front fighters standing near the Quneitra crossing between Israel and Syria. (screen capture: YouTube)

Al-Nusra Front fighters standing near the Quneitra crossing between Israel and Syria. (screen capture: YouTube)

There have been several cases of cross-border fire from the Syrian fighting over the past several days, with the Israeli army hitting back in some cases.

On Saturday, two mortar shells exploded inside Israel near the Israel-Syria border in the Golan Heights, causing no injuries or damage, according to initial reports.

The explosions were believed to be strays from fighting between rebel groups and government troops on the Syrian side of the Golan.

Times of Israel staff and AP contributed to this report.