Iran and several of its armed proxies on Monday vowed to retaliate against Israel following the alleged assassination of a senior Islamic Revolution Guards Corps commander in Syria.

IRGC commander Seyyed Razi Mousavi was killed Monday in an Israeli airstrike that targeted him a Damascus suburb, Iran's state-run IRNA reported, citing a statement from IRGC public relations.

The IDF declined to comment on the report when asked by CNN.

The IRGC vowed to avenge his killing, saying "the Israeli regime would undoubtedly pay the price for this crime."

Iranian Foreign Minister Hossein Amir-Abdollahian also warned Israel of repercussions, saying: "Tel Aviv should expect a tough countdown.”

In a separate statement, Iranian Foreign Ministry spokesperson Nasser Kanaani said Iran "reserves the right to take necessary measures and respond to his killing at the right time and in the right place.”

Israel has for years targeted what it calls Iran-linked positions in Syria, where the IRGC, an elite wing of the Iranian military, has a significant presence.

According to IRNA, Mousavi was serving as a military adviser in Syria. His alleged assassination comes at a time of heightened regional tensions over Israel's ongoing war against Hamas in Gaza, which has led to fears of a wider conflict.

Iran's warnings of retaliation were echoed Monday by Iran-backed Lebanese militant group Hezbollah and the Iran-linked al-Nujaba Resistance Movement in Iraq.

In a statement Monday, Palestinian Islamic Jihad condemned Mousavi's killing and said he “had a fundamental and pivotal role in supporting the resistance forces in the region, and supporting the Palestinian people, their resistance and their cause.”