Israel said its aircraft attacked a Syrian army position on Tuesday after a stray mortar bomb struck the Israeli-controlled Golan Heights, and it denied a Syrian statement that a warplane and drone were shot down.

The airstrike was a now-routine Israeli response to the occasional spillover from fighting in a five-year-old civil war, and across Syria a ceasefire was holding at the start of its second day.

Syria's army command said in a statement that Israeli warplanes had attacked an army position at 1 a.m. on Tuesday (2200 GMT, Monday) in the countryside of Quneitra province.

The Israeli military said its aircraft attacked targets in Syria hours after the mortar bomb from fighting among factions in Syria struck the Golan Heights. Israel captured the plateau from Syria in a 1967 war.

The Syrian army said it had shot down an Israeli warplane and a drone after the Israeli attack.

Denying any of its aircraft had been lost, the Israeli military said in a statement: "Overnight two surface-to-air missiles were launched from Syria after the mission to target Syrian artillery positions. At no point was the safety of (Israeli) aircraft compromised."

The seven-day truce in Syria, brokered by Russia and the United States, is their second attempt this year by to halt the bloodshed.