Two mortar rounds fired from Syria struck open areas of the Israeli-occupied sector of the Golan Heights on Tuesday, an Israeli source said.

"Two mortar shells fell in the northern sector of the Golan Heights," the source told AFP, saying it was a result of stray fire from fighting inside Syria and had caused no casualties or damage.

The Israeli army said that "multiple explosions" were heard in the Golan Heights and that sirens had sounded in several areas.

The mortar fire came two days after the Israeli military said the air force had targeted four "terrorists" armed with explosives who were "en route to carry out an imminent attack" on troops on the armistice line.

All four were killed.

Several hours later, in the early hours of Monday morning, there were reports of a strike on missile batteries in the Qalamun area near the Syria-Lebanon border, which were attributed to Israel.

Although the army declined to comment, an Israeli source told AFP he was "not aware of any unusual (Israeli) activity in Syria overnight" saying it was believed to be related to the ongoing civil war.

In another incident at the weekend, reports emerged early Saturday of a strike on Syrian army weapons storage facilities along the border with Lebanon, which was also blamed on Israel.

The Israeli army refused to comment.

Israel seized 1,200 square kilometres (460 square miles) of the Golan Heights in the Six-Day War of 1967 and later annexed it.

Since the Syrian conflict erupted in 2011, the plateau has been tense, with a growing number of rockets and mortar rounds hitting the Israeli side, mostly stray, prompting occasional armed responses.

*This story was edited by Ahram Online.