Russia is sending troops from the country’s far east to Belarus for major war games, officials said, in a deployment further beefing up Russian military assets near Ukraine amid Western fears of an invasion.

Deputy defence minister Alexander Fomin said the drills are intended to practice a joint response to external threats by the alliance of Russia and Belarus, which have close political, economic and military ties.

He did not say how many troops and weapons are being redeployed for the exercises.

Ukrainian officials have warned that Moscow could launch an attack from various directions, including from the territory of its ally Belarus.

The deployment would dramatically bolster an estimated 100,000 troops with tanks and other heavy weapons amassed near Ukraine in what the West fears could be a prelude to an invasion.

Moscow has denied an intention to attack its ex-Soviet neighbour, but demanded guarantees from the West that Nato will not expand to Ukraine or other ex-Soviet nations or place its troops and weapons there.

Washington and its allies firmly rejected Moscow’s demands during last week’s Russia-US negotiations in Geneva and a related Nato-Russia meeting in Brussels.

Mr Fomin said the drills, which involve an unspecified number of troops from Russia’s Eastern Military District that encompasses Eastern Siberia and the Far East, reflect the need to practise concentrating the country’s entire military potential in western Russia.

“A situation may arise when forces and means of the regional group of forces will be insufficient to ensure reliable security of the union state, and we must be ready to strengthen it,” Mr Fomin said at a meeting with foreign military attaches.

“We have reached an understanding with Belarus that it’s necessary to engage the entire military potential for joint defence.”

Belarus’s authoritarian president, Alexander Lukashenko, said the joint manoeuvres will be conducted on his western border and also in the country’s south, where it borders Ukraine.

He has increasingly relied on the Kremlin’s support amid Western sanctions over a brutal crackdown on domestic protests.

The US and its allies have urged Russia to de-escalate the situation by calling the troops back to their barracks.

“In recent weeks, more than 100,000 Russian troops with tanks and guns have gathered near Ukraine without an understandable reason, and it’s hard not to understand that as a threat,” German foreign minister Annalena Baerbock told reporters after the talks in Moscow with Russian counterpart Sergey Lavrov.

He responded by reaffirming Moscow’s argument that it is free to deploy its forces wherever it considers it necessary on its territory.

“We can’t accept demands about our armed forces on our own territory,” he said, adding that “troops’ training is something that every country does”.

“We aren’t threatening anyone, but we are hearing threats to us,” he added. “We will decide how to react depending on what specific steps our partners will take.”

Russia annexed the Crimean peninsula from Ukraine in 2014 after the removal of Ukraine’s Moscow-friendly leader, and also threw its weight behind a separatist insurgency in eastern Ukraine.

More than 14,000 people have been killed in nearly eight years of fighting there.