An Israeli warplane struck a Syrian army post on Friday, hours after stray fire from Syria's civil war hit the Israeli-occupied Golan Heights, the Israeli military said.
"In response to the projectile launched earlier today at Israel from Syria, an Israel Air Force aircraft targeted the Syrian army position that fired the mortar," the English-language Israeli statement said.
"The errant projectile was a result of internal fighting in Syria."
It was the fourth such exchange in a week as Syrian troops battle rebels, including hardline Islamists, on the other side.
There have been no casualties but Israel responded to the previous three incidents by striking Syrian government positions.
Rebels recently launched an offensive against government forces in Quneitra on the Syrian side of the armistice line.
During a speech on Wednesday, Israeli Prime Minister Benjamin Netanyahu said he would not tolerate any spillover from the fighting.
"We will respond to every firing," he said. "Whoever attacks us, we will attack him. This is our policy and we will continue with it."
He was speaking at the Israeli settlement of Katzrin on the Golan, when a Syrian mortar shell hit further north and Israeli warplanes retaliated.
"During my speech, shells from the Syrian side landed in our territory and the Israel Defence Forces have already struck back," he said.
Israel seized 1,200 square kilometres (460 square miles) of the Golan Heights from Syria in the Six-Day War of 1967 and later annexed it in a move never recognised by the international community.
Around 510 square kilometres of the Golan are under Syrian control.