As world looks to Ukraine, did Russia just take Belarus?

"The continued presence of Russian military forces at the request of the illegitimate [Belarus president Alexander] Lukashenko regime should be treated as an occupation of Belarus. This must be made absolutely clear during the ongoing US and EU talks with Russia," they added.

"Any diplomatic decision to deter possible Russian aggression against Ukraine must envisage an independent and democratic future for Belarus, not at its expense," they said.

The letter was signed by 77 MEPs from centrist, left, and right-leaning parties and from across Europe - including Denmark, France, Germany, and Sweden - as well as eastern European countries.

Russia has begun massing 30,000 troops in Belarus for a joint military drill in February called Allied Resolve 2022, which has already begun.

"These are highly capable, combat-ready troops, and there is no transparency on these deployments," Nato secretary general Jens Stoltenberg said last Friday.

And the military exercise could be a "disguise" for something else, he added.

But if the MEPs feared the Russian troops might never leave Ukraine, some in the US and Ukraine feared the Russian forces could be used to strike Kyiv, which is just 140km from the Belarusian border.

The US State Department, on Monday, urged Americans not to travel to Belarus for fear it might get dragged into a war due to Russia's deployments there.

"As a result of Russia taking control over Belarus, 1,070 km of our border with Belarus became a threat. This is not a threat from Belarus - Ukraine has a very warm attitude toward the Belarusian people - but a threat from Russia moving through Belarus," Ukrainian defence minister Oleksii Reznikov recently told The New York Times.

"The biggest danger is that Ukrainian forces are mainly concentrated in the east of Ukraine, but the closest route to Kyiv is from Belarus," Arseniy Yatsenyuk, a former Ukrainian prime minister, also said.

Meanwhile, Belarus is already under severe EU sanctions over Lukashenko's crackdown on pro-democracy protesters and his abuse of migrants to attack EU borders.

Lithuanian state railways, on Monday, said they would no longer transport Belarusian potash, its main export, to the port of Klaipeda in Lithuania in line with the EU measures.

Ryanair, one of whose planes Lukashenko's airforce hijacked last year to capture a dissident, said Tuesday: "There should be no overflight of Belarus unless appropriate guarantees are obtained that this won't recur".

And the US State Department warned, on Monday, that if Belarus facilitated Russian aggression, it would also suffer "unprecedented ... swift and decisive" new US measures.