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

"China condemns the attack," Foreign Ministry spokesperson Wang Wenbin said.

"The security of diplomatic institutions cannot be violated, and Syria's sovereignty, independence and territorial integrity should be respected," he said.

"The current situation in the Middle East is turbulent and we oppose any actions that lead to an escalation of tensions," Wang said.

The Israeli air strikes destroyed the Iranian embassy's consular annex in Syrian capital Damascus, Syrian and Iranian officials said.

A top Revolutionary Guard commander was among seven members the force said were killed.

China is a close partner of Iran and its largest trade partner and a top buyer of its sanctioned oil.

Beijing also enjoys close ties with Damascus.

In September last year it became one of only a handful of countries outside the Middle East that President Bashar Al-Assad has visited since the 2011 start of a civil war that has since killed more than half a million people, displaced millions more.

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".

China also Tuesday said it was "shocked" and condemned a strike in Gaza that a US-based charity said killed seven of its staff as they unloaded desperately needed food aid.

"China opposes all acts that harm civilians, damage civilian facilities, and violate international law," Wang said.

"We are shocked by the attack on international rescue workers in Gaza and condemn it," he said.

"We express our deep condolences to the victims," Wang added.

"Civilians should not be targets of attacks, and the safety of international humanitarian rescuers should not be threatened," he said.