Israel's military on Tuesday said it had responded with artillery fire from the Golan Heights after munitions were launched toward territory it has occupied since 1967.
"Soldiers are responding with artillery and mortar shells toward the origin of the launching in Syria," an Israeli military statement said, on the fourth day of a war with Gaza-based Hamas militants that has sent regional tensions soaring.
The military said there had been "a number of launches from Syria into Israeli territory".
A military spokesman told AFP it appeared to have been mortar fire.
This was the first exchange of fire between Israel and Syria since Hamas carried out an unprecedented assault on Israeli territory from the blockaded Gaza Strip on Saturday.
Fears of another front opening in the conflict have grown after days of clashes with militants on the northern border with Lebanon.
According to the Syrian Observatory for Human Rights, a UK-based NGO with an extensive network of sources in Syria, the shells were fired by "Palestinian factions working with the Lebanese Hezbollah".
Israel captured the Golan Heights from Syria in the Six-Day War of 1967. Its 1981 annexation of the strategic area is not recognised by the United Nations.
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