An Israeli warplane struck a Syrian army post on Friday, the Israeli military said, hours after stray fire from Syria's civil war hit the Israeli-occupied Golan Heights.

‘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, leading to occasional stray fire.

There have been no casualties on the Israeli side but the Jewish state also 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.

Israel has conducted several air strikes in Syria since that country's civil war erupted in 2011, most of which it has said had been against arms convoys or warehouses of its Lebanese arch-foe Hezbollah.

The Iran-backed movement is a key supporter of the Syrian regime and is fighting alongside government forces.

In April, Israel shot down what it identified only as ‘a target’ over the Golan, hours after Syria accused it of hitting a military position near Damascus airport.

Israel did not confirm or deny the reported Damascus attack.

Israeli Prime Minister Benjamin Netanyahu said on Wednesday that he would not tolerate any spillover from the fighting in Syria.

‘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.’

- 'Determined to respond' -

Netanyahu was speaking at the Israeli settlement of Katzrin in the Golan, when a Syrian mortar shell hit further north and the Israeli military 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.

‘Our line is clear,’ Netanyahu said in his Hebrew-language speech on Wednesday.

‘We are not interfering in the bloody conflict in Syria, which has been going on for more than six years, but we are determined to respond firmly and forcefully to any violation of our sovereignty.’

‘We shall not permit radical Islam, led by Iran or Daesh, to open a terrorist front against the State of Israel from the Syrian side of the Golan Heights,’ he added using the Arabic acronym for the Islamic State Jihadist group.

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