Gen. Mohammad Bagheri, Iran's joint chief of staff, told mourners gathered for the funeral of Gen. Mohammad Reza Zahdi that Iran will decide when and how to stage an “operation” to take revenge. Zahdi was the highest ranking commander slain in Monday's attack.

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“The time, type, plan of the operation will be decided by us, in a way that makes Israel regret what it did," he said. "This will definitely be done.”

The attack on an Iranian diplomatic compound was a significant escalation in a long-running shadow war between the two archenemies, and Israel has been bracing for an Iranian response.

In all, 12 people were killed in the strike: Seven Iranian Revolutionary Guard members, four Syrians and a Hezbollah militia member.

On Friday, the commander of Iran's powerful Revolutionary Guard, Gen. Hossein Salami, warned that “our brave men will punish the Zionist regime,” escalating threats against Israel.

Tensions have flared against the backdrop of the six-month-old Israel-Hamas war in Gaza, and raised renewed fears of a broader regional conflict. The Islamic militant group Hamas, which has ruled Gaza for 17 years, is one of Iran's proxies, along with Lebanon's Hezbollah militia and Yemen's Houthi rebels.

Both Hezbollah and the Houthis have carried out attacks along the fringes of the Gaza war, with Hezbollah engaging in daily cross-border exchanges with Israel and the Houthis frequently targeting Red Sea shipping.

Bagheri made the comments in Isfahan, Zahedi's hometown, about 440 kilometers (270 miles) south of the capital Tehran.