An Israeli warplane on Wednesday fired a rocket into the Syrian-controlled side of the Golan Heights, a monitoring group reported.
The Syrian Observatory for Human Rights added that the plane targeted an area housing a municipal administration building in southern Syria.
The Britain-based watchdog did not give casualties.
However, a Syrian security official in the area, speaking on condition of anonymity, said one civilian was killed and three Syrian soldiers were injured in the alleged airstrike that targeted a military post near al-Baath town.
There was no official confirmation either in Damascus or Tel Aviv.
Earlier this month, Israel attacked two Syrian army targets after stray fire from fighting in Syria's civil war damaged the security fence in the Israeli-controlled Golan Heights.
The Israeli military in the past has launched shells and airstrikes in response to bombs that landed in Golan during battles in the Syrian conflict.
Israel seized 1,200 square kilometres of the Golan Heights from Syria in the Six-Day War of 1967.
Meanwhile, the spokesman for the Kurdish-backed Minbij military Council, Shervan Darwish, told dpa that the Islamic State are using civilians as human shields in Minbij.
Darwish said the Kurdish-led Democratic Forces of Syria (DFS) and allied strikes on Tuesday killed 78 members of the Islamic State in the village of al-Tukhar al-Kabir north of Minbij, an Islamic State-held city in northern Syria that is the focus of a US-backed campaign by Kurdish-led ground forces.
He said the strikes also killed civilians who were taken by the jihadist movement as "human shields" in the area, but did not specify the number.
"We regret it ... (killing of civilians) despite our commitment to the protection of civilians," he said.
On Tuesday, the Britain-based Syrian Observatory for Human Rights said at least 56 civilians were killed in airstrikes launched by a US-led coalition near Minbij.
The watchdog said that the planes hit the area by mistake.
The Pentagon said they were looking into the reported casualties in the village of al-Tukhar al-Kabir.
Some activists who are from Minbij put the death toll at over 100.
If confirmed this would be the highes civilian death toll since the US-led coalition against Islamic State began air operations in Syria in 2014.
The DFS have besieged Minbij since early June in an attempt to cut off Islamic State's access to the nearby Turkish border. Islamic State fighters have resisted fiercely in street fighting inside the city and have staged diversionary attacks from surrounding areas that remain under their control.
In statement late Wednesday the opposition Syrian National Coalition which already condemned Tuesday's airstrikes, called for halting the US allied strikes to protest the killing of civilians in Minbij.
"We call for the immediate halting of allied military operations in Syria to allow a thorough investigation into these incidents," the statement said, adding that the investigations should not only lead to review the procedural rules, but hold those responsible accountable.
He added that recurrence of these incidents would indicate " a clear imbalance in the operational rules" followed by the allied strikes in populated areas.
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