International sports federations should either move or cancel sports events currently planned in Russia or Belarus, the International Olympic Committee (IOC) said on Friday, a day after Russia invaded Ukraine.

Russian troops entered Ukraine through Belarus when the invasion began on Thursday. Ukraine's chief of staff said on Friday that the Russians were now using an airfield in Belarus to line up troops to assault Kyiv.

"The Executive Board (EB) of the International Olympic Committee reiterated today the IOC's strong condemnation of the breach of the Olympic Truce by the Russian government and the government of Belarus through its support in this," the IOC said in a statement.

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It said international sports federations "should take the breach of the Olympic Truce by the Russian and Belarusian governments into account and give the safety and security of the athletes absolute priority."

The IOC's executive also said that Russian and Belarusian national flags should not be displayed at international sports events.

Russian athletes at the Beijing Games did not compete under their flag and their anthem was not played at any ceremonies, following sanctions imposed for the widespread doping across many sports exposed after the 2014 Sochi Games.

The invasion of Ukraine led to Russia losing the Champions League final, the Formula One Russian Grand Prix and skiing World Cup events among many others.