Syrian and pro-Iranian officials have accused Israel of being behind nighttime strikes on the posts of Iranian-backed militias in eastern Syria that are reported to have left at least 18 fighters dead.
A Syrian security official told the Associated Press that Israel was behind the attacks, but said there were no casualties.
An official with an Iranian-backed militia in Iraq also blamed Israel for the air strikes that hit in the eastern Syrian town of Al Bukamal early Monday. There was no immediate comment from Israel, which rarely admits to its military actions in the Middle East and views Iran as its greatest threat.
It has allegedly struck Iran-linked targets as far away as Iraq in recent weeks.
The attack comes amid rising tensions in the Middle East and the crisis between Iran and the US in the wake of the collapsing nuclear deal between Tehran and world powers.
Israel frequently attacks Iranian targets in Syria and is believed to have recently crash-landed drones in southern Beirut in a stronghold of the Iranian-backed Hezbollah group.
Israeli Prime Minister Benjamin Netanyahu said last month that Iran has no immunity anywhere and that the Israeli military forces "will act – and currently are acting – against them".
According to the Britain-based Syrian Observatory for Human Rights, the airstrikes began late Sunday and continued after midnight, killing 18 Iranian and pro-Iranian fighters and also causing extensive damage.
Meanwhile, the Israeli military said rockets launched from Syria on Monday fell short and did not land in Israel. The military said the rockets were launched from the outskirts of Damascus by Shiite militants operating under the Iranian Revolutionary Guard. The military said it holds the Syrian government responsible for the attempted attack.