Syrian rebels and a monitoring group said two explosions that struck a Syrian town near the Israeli-occupied Golan Heights on Wednesday were caused by an Israeli air strike but Lebanon's Hezbollah blamed rocket fire by al Qaeda-linked militants.
At least one blast struck near the governorate building in Baath City, capital of the southern province of Quneitra which borders the Golan region.
The town is held by pro-Syrian government forces, including the army and Hezbollah fighters. The Nusra Front, Western-backed rebels, and groups which have pledged allegiance to Islamic State also operate in the region.
A Syrian military source said two rockets had hit the town but their origin was unknown. "There is information that there was a rocket which fell on one of a government headquarters in Quneitra in the area of the town of Baath," he said.
Two Syrian rebels said an Israeli jet had been seen circling the area and carried out an air strike on a military position.
"Our information is that the attack targeted a Hezbollah outpost," said Maher al Ali, a spokesman for the Syrian Revolutionaries Front, a Western-backed rebel group.
The Syrian Observatory for Human Rights monitoring group said an Israeli jet fired a rocket near the governorate building. It said it had no information on casualties.
Hezbollah said Nusra Front fired two rockets loaded with high explosives towards Baath City, causing civilian deaths. "The Israeli enemy was monitoring the launchpoint of the rockets next to the Nusra positions. There is no truth to (reports of) any raids by the Israeli enemy," it said.
An Israeli military spokeswoman said: "We do not respond to reports of this kind."
Though formally neutral on the civil war, Israel has targeted Hezbollah officials and arms convoys inside Syria several times during the conflict.
In January last year it carried out a helicopter attack in Quneitra province that killed a top Iranian Revolutionary Guard general and several Hezbollah members including a son of the group's late military commander, Jihad Mughniyeh.
Wednesday's incident took place three days after Israel said it fired missiles towards an unmanned drone that briefly entered Israeli-controlled airspace from Syria.
The Golan Heights is a strategic plateau that Israel captured from Syria in the 1967 Middle East war, and annexed in a move that has not won international recognition.