Iran accused Israel on Monday of killing a high-level military figure in a missile strike in Syria at a time when concerns are growing that the war in the Gaza Strip could escalate into a regional conflict.

The assassinated Iranian was identified as Brigadier General Sayyed Razi Mousavi, a senior adviser to Iran’s Revolutionary Guard. He was said to have helped oversee the shipment of missiles and other arms to Hezbollah, the Iranian-backed military force in Lebanon and Syria that is a frequent adversary of Israel’s.

Israel, adopting its customary stance, declined to comment directly on the accusations, but Israeli officials acknowledged that they were preparing for the prospect of Iranian retaliation.

Israel is already waging a major war in Gaza and skirmishing with Hezbollah fighters on its northern border with Lebanon. And on the Red Sea, in response to the Gaza conflict, Yemen-based Houthi forces — also backed by Iran — have been widening the conflict by targeting vessels.

In confirming Mousavi’s killing, on a farm outside Damascus, Syria, Hezbollah described him as a “dear brother”. The semi-official Iranian news agency Fars said that Israel would “pay for this crime without a doubt”. Various news outlets said he was killed on Monday.