"Chinese nationals currently in Iran are advised to strengthen safety precautions and evacuate as soon as possible," the foreign ministry said in a social media statement.

The United States on the same day authorised the departure of non-emergency embassy staff from Israel, as it threatened strikes on Iran and pressed its biggest military build-up in the Middle East in decades.

This came a day after Oman-mediated talks between Iran and the US -- which have been seen as a last-ditch bid to avert war -- though initial optimism was tempered by Tehran warning Washington must drop "excessive demands" to reach a deal.

Beijing's foreign ministry told its citizens on Friday to avoid travelling to Iran for the time being "in light of the current security situation".

The foreign ministry added that its Chinese embassies and consulates in Iran and neighbouring countries will provide "necessary assistance" to Chinese citizens seeking to relocate via commercial flights or overland routes.