The Israeli army has fired what it called "warning shots" into Syria after a mortar round landed inside an army post in the Israeli-occupied Golan Heights, in the first Israeli fire directed at the Syrian military since 1973.
The army warned in a statement that "fire emanating from Syria into Israel will not be tolerated and shall be responded to with severity."
Live Box 2011421105226899357
An Israeli security source said the military fired a single Tamuz anti-tank missile, a weapon known for being highly accurate, in the direction of a Syrian army mortar crew.
"We shot toward them, but deliberately missed," Israeli military sources told the AFP news agency.
The Syrian troops had launched a shell which overshot the Golan disengagement fence, exploding near a Jewish town without causing casualties.
The army said it had filed a complaint with United Nations forces operating in the area. There was no immediate comment from the 1,200-strong United Nations Disengagement Observer Force which has patrolled the Golan since 1974.
Prime Minister Binyamin Netanyahu, speaking in Jerusalem, warned that Israel would retaliate to any more cross-border fire.
"We are closely monitoring what is happening on our border with Syria and there too we are ready for any development," he told his ministers at the beginning of the weekly cabinet meeting.
Series of Golan exchanges
Sunday's cross-border fire was the latest in a string of incidents in which the fighting in Syria's ongoing bloodshed has spilled across the ceasefire line.
More than 37,000 people have lost their lives since the uprising against Syrian President Bashar Assad's rule erupted in March last year, according to the Syrian Observatory for Human Rights.
On Thursday, three stray mortar rounds from Syria hit the Golan, which Israel seized from Syria in the 1967 Middle East war and annexed in 1981 in a move never recognised by the international community.
And on Monday, an Israeli military vehicle patrolling the buffer zone was hit by gunfire, with the army saying it was caused by "stray bullets" from Syria.
No one was wounded, but the incident prompted an Israeli complaint to the United Nations Security Council in which it described the gunfire as a "grave violation" of a 1974 agreement on security in the buffer zone.
Two days earlier, three Syrian tanks entered Bir Ajam village, five kilometres southeast of Quneitra, in the demilitarised zone, sparking another Israeli complaint to the UN.
Mortar rounds from Syria have landed inside the Golan at least three times over the past ten days.
Turkish border clashes
Meanwhile, Syrian helicopters and artillery have bombarded the Ras al-Ain area near the border with Turkey, days after Free Syrian Army rebels captured it during an advance into the northeast, activists said.
Helicopters fired rockets at a grain storage area near the village of Tal Halaf and shells hit the border crossing in the northeastern oil-producing province of Hasaka, home to a large number of Syrian Kurds.
Syrian warplanes also launched air strikes on the eastern town of Abu Kamal near the Iraqi border and pounded
rebel lines near Damascus and in the northern city of Aleppo, the Syrian Observatory for Human Rights, an activist group, said.
Two civilians were reportedly killed in air raids on Abu Kamal, while several districts of Deir Ezzor city were shelled by tanks.
Live Box 20117693233259422
The Observatory also reported clashes between President Bashar al-Assad's forces and rebels during the night in the town of Harasta on the northeastern outskirts of Damascus.
The Local Co-ordination Committees, a network of opposition activists on the ground, meanwhile, reported heavy shelling overnight by regime forces on rebel areas southwest of the capital and in the town of Yabrud to the north.
In the northern city of Aleppo, where fighting between rebels and government troops has raged since mid-July, mortars rained down on the rebel bastions of Shaar in the east, Sukari in the south and Halab al-Jadida in the west, according to the Observatory.
Residents said fierce clashes erupted in the northwest districts of Zahraa and Liramun, where tanks fired on rebel positions, and in the embattled Old City.
The Observatory reported army shelling Sunday of the strategic rebel-held town of Maarat al-Numan, the nearby village of Maarshmisha and Idlib city in the northwest province of Idlib.
The army on Saturday retook a stretch of the Damascus-Aleppo highway in Idlib province used to send its reinforcements to main northern battlefields, but has failed to regain control of Maaret al-Numan.