Israeli air strikes destroyed the Iranian embassy's consular annex in Damascus Monday, Syrian and Iranian officials said, with a top Revolutionary Guard commander among seven members the force said were killed, amid worsening regional tensions.

Israel said it would not comment on the reported attack, but Iranian officials vowed a stiff response with fears of even further violence between Israel and Iran's allies triggered by the Gaza war.

Iran's Islamic Revolutionary Guard Corps named Brigadier General Mohammad Reza Zahedi and another high-ranking officer, Brigadier General Mohammad Hadi Haji Rahimi, as among seven of its members killed.

Britain-based war monitor the Syrian Observatory for Human Rights said 11 people, including several Guards members, were killed when "Israeli missiles... destroyed the building of an annex to the Iranian embassy".

The toll includes "eight Iranians, two Syrians and one Lebanese -- all of them fighters, none of them civilians," Rami Abdel Rahman, who heads the Observatory with a network of sources in Syria, told AFP.

Iran's ambassador to Syria, Hossein Akbari, giving a lower toll, told Iranian state TV that "at least five people were killed in the attack which was carried out by F-35 fighter jets" which fired six missiles at the building.

AFP reporters saw the annex building had caved in, and emergency services were rushing to search for victims under the rubble as sirens wailed in the upscale Damascus district of Mazzeh.

Security personnel shielded the site where earth-moving equipment was brought in to clear the debris and remove charred vehicles from the road outside, watched by a crowd of onlookers.

Syria's defence ministry said "the attack destroyed the entire building, killing and injuring everyone inside, and work is underway to recover the bodies and rescue the wounded from under the rubble".

- Regional tensions -

Iranian state TV said Zahedi -- a senior commander of the Islamic Revolutionary Guard Corps' foreign operations arm, the Quds Force -- was among the dead.

The Observatory said Zahedi served as the leader of the Quds Force for Palestine, Syria and Lebanon, adding that he was killed along with his deputy, his aide, and the Quds force chief of staff for the same three countries.

Two other members of the Guards and two Iranian advisers were also killed in the strike, the Observatory said.

The targeted building is next to the Iranian embassy, the front of which is decorated with a large portrait of Qassem Soleimani, the architect of Iran's military operations in the Middle East, killed in January 2020 in an American drone strike in Iraq.

The Damascus strikes were the fifth in a week to hit Syria, whose President Bashar al-Assad is supported by Iran, Israel's long-time arch foe in the region.

Syria's state news agency SANA had earlier reported that "our air defence systems confronted enemy targets in the vicinity of Damascus".

Iran's ambassador, Akbari, vowed the attack "will lead to our decisive response", adding "the Israeli attack on the Iranian consulate shows the reality of the Zionist entity which recognises no international laws and does all that is inhumane to achieve its goals".

Iranian Foreign Minister Hossein Amir-Abdollahian called for a "serious response by the international community".

- 'Heinous attack' -

Only the gate of the building was left standing after the attack, with a sign mentioning "the consular section of the embassy of Iran", an AFP journalist said.

Window panes in buildings within a 500-metre (550 yard) radius had been shattered, and many parked cars were damaged by the blast.

Syrian Foreign Minister Faisal Mekdad also denounced the attack after visiting the site, calling it a "heinous terrorist attack... killing a number of innocent people", in a statement carried by SANA.

The Gaza war, which started with the October 7 Hamas attack on southern Israel, has devastated the coastal territory and also seen Israel and Lebanon's Iran-backed Hezbollah exchange near daily cross-border fire.

Israel has also struck targets in Syria, mostly army positions as well as those of Iran-backed combatants.

Hamas condemned "in the strongest terms" the attack which it called a "dangerous escalation."

Moscow, a Damascus ally along with Tehran, blamed "the Israeli Air Force" for the "unacceptable attack against the Iranian consular mission in Syria."

The Damascus strike came three days after the Observatory reported Israeli strikes that had killed 53 people in Syria, including 38 soldiers and seven members of Hezbollah.

It was the highest Syrian army toll in Israeli strikes since the Israel-Hamas war began, said the monitor.

"Syria and Lebanon have become one extended battleground from the Israeli perspective," Riad Kahwaji, head of the Institute for Near East and Gulf Military Analysis, told AFP after the Friday strikes.

The bloodiest ever Gaza war erupted with the Palestinian militants' unprecedented October 7 attack which resulted in about 1,160 deaths in Israel, mostly civilians, according to an AFP tally of Israeli official figures.

Israel's retaliatory campaign, aimed at destroying Hamas, has killed at least 32,845 people, mostly women and children, according to the Gaza health ministry.