DAMASCUS/BEIRUT, Jan 20 (Reuters) -

Three Iranian Revolutionary Guards officers killed in an Israeli strike that flattened a building in Damascus on Saturday were described in Iranian state media with an honorific used only for generals, suggesting the targets were senior commanders.

Tehran vowed on Saturday to take revenge on Israel after the strike which it said killed five Guards and an unspecified number of Syrian troops.

Ambulances and fire trucks gathered around the site of the strike, which had been cordoned off, a Reuters journalist at the scene said. Rescue operations for people stuck under the rubble continued through the day. A crane was in place to hoist concrete slabs off the wreckage.

A security source in a network of groups close to Syria's government and its ally Iran told Reuters the multi-storey building was used by Iranian advisers supporting President Bashar al-Assad's government. It was completely flattened by "precision-targeted Israeli missiles", the source said.

Portraits of the five Revolutionary Guards carried on Iranian state media referred to three of them with an honorific used for generals, while the others were a major and someone holding a lower rank. The security source said one of the generals was head of information for the elite force.

"The Islamic Republic will not leave the Zionist regime's crimes unanswered," President Ebrahim Raisi said in a statement condemning the strike, state broadcaster IRIB reported.

Foreign Minister Hossein Amirabdollahian said on the X: "The activities of Iran's military advisers in the fight against terrorism and securing the region will continue with full strength."

There was no comment from Israel, which has long pursued a bombing campaign against Iran's military and security presence in Syria but typically does not discuss such attacks publicly.

It has killed Iranian Guards in several such strikes in a stepped-up campaign in the wake of the Oct. 7 attack on Israel by militants of the Iranian-backed Palestinian Islamist group Hamas from Gaza.

Syrian state media reported an Israeli "aerial attack" on a building in the Mazzeh neighbourhood of Damascus and said Syrian air defences had shot down a number of missiles.

Essam Al-Amin, head of the Al-Mowasat Hospital in Damascus, told Reuters that his hospital had received one dead body and three wounded people, including a woman, following Saturday's attack.

Palestinian Islamic Jihad, an Iranian-backed Palestinian faction present in Syria and Lebanon, condemned the air strike but told Reuters that none of its members were wounded, dismissing reports that some were at the bombed-out building.

Iran and its military allies in Syria have entrenched themselves in wide areas of eastern, southern and northern Syria and in several suburbs around the capital.

In December, an Israeli air strike killed two Guards members, and another near Damascus on Dec. 25 killed a senior adviser to the Guards who was overseeing military coordination between Syria and Iran.

Israel responded to the Hamas assault on southern Israel on Oct. 7 by unleashing a devastating air and ground war in Gaza with the aim of eradicating its ruling Islamist group. The conflict has reverberated across the Middle East with violence surging in Syria, Lebanon, northern Iraq and in the Red Sea.

In Lebanon, the Iranian-backed Hezbollah as well as local wings of Palestinian militant groups have fired rockets across the border at Israel in solidarity with Palestinians in Gaza.

On Saturday, an Israeli strike in south Lebanon killed a member of Hezbollah and one other Lebanese national as they were travelling in their car, two security sources told Reuters, after earlier saying two Hamas members were killed. (Reporting by Kinda Makieh and Firas Makdesi in Damascus, Laila Bassam in Beirut and Nayera Abdallah in Dubai Writing by Maya Gebeily, Angus McDowall Editing by Mark Heinrich, Angus MacSwan, Peter Graff)