Speaking to military graduates and officers, Lukashenko said he discussed the alleged Western plot with Russian President Vladimir Putin on Monday.

"Strategic plans for an attack against Russia are being developed," Lukashenko alleged, saying the West would seek to target Russia "through Ukraine and through Belarus".

"History is repeating itself," he said, in an apparent reference to the invasion of Russia by Napoleon's troops in 1812 and by Nazi Germany in 1941.

Putin sent troops into Ukraine on February 24.

Belarus, the Kremlin's main ally, has served as a staging ground for the Russian army in its offensive on neighbouring Ukraine.

Western countries have never publicly said they are planning to attack Russia.

But Lukashenko pointed to NATO's continued expansion, saying the "newly-minted crusaders" were "forming an armoured fist" to attack Russia.

"The events unfolding today around Belarus and Russia call for our utmost vigilance and concentration," Lukashenko said.

He said the West was pushing the world towards "major war" and said the army should "keep its powder dry".

Russian foreign ministry spokeswoman Maria Zakharova struck a similar note on Tuesday.

She accused the United States and its allies of provoking the Ukraine crisis and risking "an open military confrontation with our country".

"Obviously, such a collision would carry a risk of nuclear escalation," she said in a statement.