China said on Friday it was "deeply concerned" over Israeli strikes on Iran – including nuclear and military sites – condemning "violations" of the country's sovereignty and offering to help ease tensions.

"The Chinese side... is deeply worried about the severe consequences that such actions might bring," Foreign Ministry spokesman Lin Jian said.

"The Chinese side calls on relevant parties to take actions that promote regional peace and stability and to avoid further escalation of tensions," Lin said.

The attacks have killed the country's armed forces' chief of staff, the head of Iran's Revolutionary Guards and top nuclear scientists.

The Israeli military said later that Iran launched 100 drones towards Israel in response and that its air defences were intercepting them outside Israeli territory.

Elsewhere, Nato Secretary General Mark Rutte said it was "crucial" for allies of Israel to work to de-escalate tensions.

"I know that they are doing that and I think that is now the first order of the day," Rutte told reporters at a press conference in Stockholm.

The EU foreign policy chief Kaja Kallas has also called for all sides to "exercise restraint".

"The situation in the Middle East is dangerous... Diplomacy remains the best path forward, and I stand ready to support any diplomatic efforts toward de-escalation," Kallas wrote on X.

Germany's leader Friedrich Merz, meanwhile, said both sides should refrain from steps that could destabilise the entire region.

Merz said he had been briefed by Israeli Prime Minister Benjamin Netanyahu about the raids and had convened a meeting of Germany's security cabinet.

"Germany stands ready to use all diplomatic means at our disposal to influence the parties to the conflict. The goal must remain that Iran does not develop nuclear weapons," he said.

Iran has repeatedly denied accusations from Western countries that is seeking to develop a nuclear weapon. (AFP)