Israel said on Saturday it had targeted Syrian military installations after shells landed in the occupied Golan Heights but a Syrian military source said the Israeli strikes killed some civilians.

Rebels including hardline Islamist factions fought the Syrian army on Saturday in Quneitra province, bordering the Israeli-occupied Golan Heights, Syrian state media and a war monitor reported.

Israel's military said 10 projectiles from inside Syria had hit the Golan and it responded with air strikes on the position they were launched from and on two Syrian army tanks, one as it was preparing to fire.

Aerial video footage released by the Israeli military purporting to show the strikes showed a machine gun and two tanks targeted and hit.

The military described the shellfire into the Israeli-held territory as errant fire and called it an "unacceptable breach" of sovereignty.

The Syrian military source said Israeli rocket fire had hit a residential building, causing a number of deaths and damage. The source did not mention Syrian fire into Israel and said the Israeli strike was in support of jihadist rebels.

The war monitor, the Syrian Observatory for Human Rights, said rebel groups in Quneitra had launched an assault and were storming army positions near Baath City.

Israel has targeted Syria several times during the conflict, sometimes after projectiles have landed in the Golan Heights, but also to hit weapons supplies of Lebanon's Hezbollah group, which is fighting alongside the Syrian government.

Syria's civil war, between President Bashar al-Assad and rebels seeking to oust him, has lasted six years, killed hundreds of thousands and pushed millions to flee their homes.