GOLAN HEIGHTS (AFP) -- Syrian troops and Islamist rebels battled close to the armistice line with Israel in the Golan Heights on Monday, as the UN pressed efforts to free 44 peacekeepers held by the insurgents.
The unrest on Israel's doorstep followed a spillover of mortar and gunfire into Israeli-occupied territory, putting the Israel on high alert and prompting it to shoot down a drone over the occupied plateau on Sunday.
Several mortar rounds struck on the edges of the ceasefire line early Monday as the combatants exchanged rocket, mortar and tank fire near the Quneitra crossing, which al-Qaeda-linked rebels seized last week, an AFP correspondent reported.
Israel had closed off the area around the crossing after an officer was wounded by stray fire last Wednesday when insurgents led by the al-Nusra Front took over the crossing into the Israeli-occupied sector of the Golan.
The Syrian Observatory for Human Rights, a Britain-based monitoring group, said Nusra fighters were locked in fierce clashes with government troops for control of the Hamidiyeh area in Quneitra, the army's remaining stronghold there.
Al-Watan newspaper, which is close to the Syrian regime, said the army was "confronting attempts by al-Nusra fighters and other terrorist groups" to take control of Hamidiyeh.
Meanwhile the UN was working to locate and release 44 Fijian peacekeepers whom the insurgents captured while they overran Quneitra, as 72 Filipino members of the same force escaped a rebel siege on their positions nearby.
The Fijians were "safe" but their whereabouts uncertain, a military official said Saturday, indicating there was contact with the group that was holding them.
And after a seven-hour firefight, 40 Filippino peacekeepers slipped away under cover of night after rebels rammed their Golan Heights outpost with armed trucks, the Philippine military said Sunday.
More than 30 other Filippino troops had reached safety Saturday.Israel watches
Israel said it shot down a drone over the Israeli-occupied sector, with the army warning in a statement it would "respond to any violation of our sovereignty."
Defense Minister Moshe Yaalon toured the region on Sunday, as the army sent reinforcements along the armistice line and deployed armored troop carriers, an AFP photographer said.
Yaalon warned that Israeli "tolerance" should not be tested.
"These past weeks we have proven that our tolerance is minimal when our integrity is struck, either intentionally or unintentionally," he said.
There has been repeated fire across the ceasefire line since the uprising in Syria erupted in March 2011, not all of it stray.
In June, Israeli warplanes attacked Syrian military headquarters and positions after an Israeli teenager was killed in what Israel said was a cross-border attack by forces loyal to Syrian President Bashar Assad.
Israel seized 1,200 square kilometers (460 square miles) of the Golan Heights during the Six-Day War of 1967, then annexed it in 1981 in a move never recognized by the international community.
The UN peacekeepers are part of a mission that has monitored the Israel-Syria ceasefire on the strategic plateau since 1974.
Peacekeepers were detained twice last year before being released safely.
The Philippines said before the latest incident that it will repatriate its 331-strong contingent for security reasons, mirroring previous moves by Australia, Croatia, and Japan.
The UN Disengagement Observer Force currently has 1,200 peacekeepers from the Philippines, Fiji, India, Ireland, Nepal, and the Netherlands.