Reuters - Chinese foreign ministry spokesperson Wang Wenbin said on Monday that all sides should remain calm and avoid further escalation, after Russian President Vladimir Putin put his country's nuclear deterrent on high alert.

Wang, speaking at a regular daily media briefing, also reiterated China's view that all countries' legitimate security concerns should be taken seriously.

Putin put Russia's nuclear deterrent on high alert on Sunday, which the United States said served to escalate the war with "dangerous rhetoric".