Ukraine may have to face a new front in the war against Russia after Belarus announced a new military link up with Russian forces.
Belarusian President Alexander Lukashenko said on Monday that some of his country's 60,000-strong army will deploy alongside Russian troops in Belarus.
The announcement came just hours after Russia launched its largest series of air strikes against Ukraine since the beginning of its invasion, killing at least 11 people in cities across the country.
Mr Lukashenko, one of Vladimir Putin's closest allies, claimed Ukraine had been preparing to attack Belarus, without providing any evidence.
"I have already said that Ukraine today it is not just discussing but planning strikes on Belarusian territory," he said during a security meeting in the capital of Minsk, according to the BelTA news agency.
"Of course, the Ukrainians absolutely do not need this. Well, why should they open a second front on our southern borders — on their northern ones?
"From the military point of view this is madness."
The authoritarian leader, who has been in power in Belarus for more than 27 years, met with Mr Putin in St Petersburg on Friday but said the decision to deploy the joint military group came following the attack on the Crimea Bridge on Saturday.
"Their (Ukraine's) owners are pushing them to start a war against Belarus to drag us there," Mr Lukashenko said.
"We have been preparing for this for decades.
"If necessary, we will respond."
Belarus' Defence Minister Victor Khrenin has ruled out active participation in the war in Ukraine.
"We don't want to fight Lithuanians, or Poles, or Ukrainians," Mr Khrenin said in a video statement on Monday.
Belarus shares a 1,000km-long border with Ukraine along its south, and attacking Ukraine from there could provide Russia with access to western parts of Ukraine, including the city of Lviv.
Russian forces used Belarus as a staging post for the February 24 invasion of Ukraine, travelling south through Ukraine's northern border to try and encircle Kyiv.
It is also believed Belarus has been used as a launch pad for missile and drone strikes against Ukraine.
Alexander Alesin, an independent Belarusian military analyst, says Belarus could host some 10,000-15,000 Russian troops, which together with its own military could form a joint force of up to 60,000. But, he argued, Minsk is not willing to deploy troops to Ukraine.
Mykhailo Podolyak, an adviser to Ukrainian President Volodymyr Zelenskyy, said Mr Lukashenko "continues to sell Russia the last crumbs of sovereignty".
"The application to place a Russian contingent in Belarus under false pretences is the formalisation of the occupation," he wrote on Twitter, adding that Ukraine does not believe there is an imminent threat of invasion from Belarus.
EU warns Belarus of possible sanctions
The European Commission warned Belarus to stop helping Russia, urging the country to refrain from any involvement in Russia's "brutal illegitimate undertaking".
"Any further actions and in particular the Belarusian military's direct involvement into this war, against the will of the vast majority of the Belarusian people, will be met by new and strong restrictive measures," commission spokesman Peter Stano said.
Mr Lukashenko's announcement has led to Poland telling its citizens to leave Belarus, following similar advice it gave last month to Poles in Russia.
"We recommend that Polish citizens staying on the territory of the Republic of Belarus leave its territory with available commercial and private means," the government said in guidance for travellers on its website.
Poland's Deputy Interior Minister Maciej Wasik has said Polish authorities are checking the country's bomb shelters; action that was planned "some time ago".
"We have 62,000 such facilities across the country," Mr Wasik told broadcaster Polsat News.
"Firefighters are checking their condition, whether they are equipped, and whether they are fit for use.
"If not, we will take steps to adapt them."
