The two Middle Eastern powers exchanged fire on Saturday, a day after Israel unleashed an unprecedented aerial bombing campaign that targeted Iranian nuclear and military facilities.

International calls for restraint are multiplying as fears grow the region could be on the threshold of a broader conflict.

China's foreign ministry released separate statements late on Saturday announcing Wang's phone calls with his counterparts.

Wang first spoke to Iranian Foreign Minister Abbas Araghchi, telling him Beijing "supports Iran in safeguarding its national sovereignty, defending its legitimate rights and interests, and ensuring the safety of its people".

China enjoys close ties with Iran -- Beijing is its largest commercial partner and the main buyer of its oil, with Tehran still under crushing US sanctions.

Wang told Araghchi that Israel's actions "seriously violate... the basic norms governing international relations", and noted the attacks on Tehran's nuclear facilities "have set a dangerous precedent with potentially catastrophic consequences".

A second statement released shortly afterwards detailed Wang's talk with Israeli Foreign Minister Gideon Saar.

Wang told Saar that "China clearly opposes Israel's violation of international law by attacking Iran with force", calling its behaviour "unacceptable".

Wang recounted his phone call with Araghchi to Saar, the statement said.

"Diplomatic means for the Iranian nuclear issue have not been exhausted and there is still hope for a peaceful solution. Force cannot bring lasting peace," Wang was quoted as saying.

He told both men that China was willing to play "a constructive role" in de-escalating the conflict.