Russian President Vladimir Putin on Wednesday denounced Western silence on Belarusian strongman Alexander Lukashenko's claim that his security services had thwarted an alleged US plot to assassinate him.

Lukashenko said on Saturday that Russian authorities had helped derail a plot to overthrow the Belarusian government and arrested two Belarusian nationals in Moscow.

He claimed senior US politicians were involved in the alleged plot, saying no one but top leadership "can assign the task of eliminating a president".

"Everyone pretends that nothing is happening at all," Putin said in his annual state of the nation address on Wednesday, referring to Western countries.

"What would have happened if the coup d'etat attempt had been actually undertaken? How many people would have suffered?"

On Saturday, Russia's Federal Security Service (FSB) said in a statement that it detained two Belarusians who planned to stage a "military coup" in Belarus and "kill" the Belarusian leader.

Lukashenko, who has ruled Belarus since 1994, thanked Putin for his help and claimed that the Kremlin chief had discussed the affair with US President Joe Biden last week.

The 66-year-old Belarusian leader has faced down historic protests against his rule, which erupted after he claimed a sixth presidential term last August, claiming to have thwarted a Western-led revolution.

Putin has backed him in the crisis and the two are set to meet in Russia on Thursday.

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