Israeli warplanes carried out airstrikes targeting Syrian army positions near the capital and Iran-backed fighters Thursday, killing 23, according to a monitoring group.

The airstrikes began after midnight and hit military bases and Iran-backed militiamen west and south of Damascus, said the Britain-based Syrian Observatory for Human Rights, which tracks the Syrian civil war through activists on the ground.

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The group said 15 Iranian-backed militiamen, including five Syrians and at least three Iranians were killed, as well as eight Syrian regime soldiers.

A "large number of missiles" triggered a fire at the Scientific Research Center in the Damascus suburb of Jamraya, the SOHR said.

Israel has not commented on the attack. The Israeli government does not usually comment on reports of its airstrikes in neighboring Syria. Iranian-backed fighters have joined Syrian government forces in the country's ongoing civil war, worrying Israeli leaders who remain cautious about having an Iranian presence near its borders.

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In December, Israel conducted an airstrike into Syria and has repeatedly target Iran-linked targets in the country.

Syrian forces backed by Iran and Russia have captured dozens of towns and villages in recent weeks, the BBC reported. More than a half-million civilians have been displaced because of the fighting.