Belarusian President Alexander Lukashenko says that Russia has agreed to offer security assistance in the case of external military threats.
Mr Lukashenko also voiced concerns over Nato military exercises taking place in neighbouring Poland and Lithuania.
The news comes as the embattled president faces mass protests over the disputed 9 August election.
Thousands gathered outside state television on Saturday, demanding full coverage of the demonstrations.
Protests are set to continue on Sunday. A “March for Freedom” is planned in the centre of the city in the afternoon.
Also a pro-government demonstration has been called for midday local time (10: 00 GMT).
“All those who love their Motherland and are against splitting the country into two opposing sides will gather for this rally,” organising group Belaya Rus said on Facebook.
However, there are reports of state sector workers being forced to attend the rally or face the threat of losing their jobs. For days, workers at state-run factories have staged walkouts and many have joined street marches against the president.
The unrest erupted after President Alexander Lukashenko claimed a landslide victory in last week’s election, the result of which has been condemned amid widespread allegations of vote-rigging.
The Central Election Commission says Mr Lukashenko, who has been in power since 1994, won 80.1% of the vote and the main opposition candidate Svetlana Tikhanovskaya 10.12%.
But Ms Tikhanovskaya insists that where votes were properly counted, she won support ranging from 60% to 70%.
How will Russia respond?
Russian TV news bulletins have been making ominous parallels between Belarus 2020 and Ukraine 2014.
Ukraine’s pro-Western revolution led to Moscow sending in its special operations forces to annex Crimea and Russian military intervention in eastern Ukraine.
Six years on, could Russia’s military intervene in Belarus?
On paper, at least, such a move would appear counter-productive. The opposition movement in Belarus is not anti-Russia/pro-Europe – it is anti-Lukashenko. If Russia were to send in troops to shore up the Belarusian leader, it risks alienating the Belarusian people and creating anti-Moscow sentiment.
True, Moscow is determined to keep Belarus within what it sees as Russia’s sphere of influence. The Kremlin’s ultimate goal is deeper integration with its neighbour – a fully-fledged union state (with Vladimir Putin at the helm). It could still achieve this through political leverage.
The Kremlin has a pathological fear of “coloured revolution” on its doorstep. But Minsk 2020 is not Kyiv 2014. Belarus is not choosing between East and West. The Belarusian people are outraged by the brutality of their security forces. So much so that even Mr Lukashenko’s traditional base – including the state factory workers – are deserting him.
What’s happening politically?
As the unrest continued on Saturday, Mr Lukashenko sought help from Russian President Vladimir Putin.
Mr Lukashenko said President Putin had promised to provide what he called comprehensive assistance in the event of external military threats to Belarus.
According to a Kremlin statement, the leaders had “said they were sure that all the problems would be dealt with in the near future”, but made no mention of a Russian offer of assistance. It emphasised that the conversation had taken place on the initiative of the Belarusian side.
Mr Lukashenko’s announcement came the day after EU foreign ministers agreed to prepare new sanctions against Belarusian officials responsible for “violence, repression and the falsification of election results”. The US has also condemned the election as “not free and fair”.
In a joint statement on Saturday, meanwhile, the prime ministers of three Baltic republics – Latvia, Lithuania and Estonia – “expressed deep concern at the violent crackdown… and the political repression of the opposition by the authorities”.
Lithuania and Latvia have previously said they are prepared to mediate in Belarus, provided the authorities stopped violence against protesters and formed a national council with members of civil society. They warned that the alternative was sanctions.
The leaders said the presidential election was “neither free nor fair” and called for a “transparent” vote “with the participation of international observers”.
Ms Tikhanovskaya left for Lithuania following the election after she publicly denounced the results. She had sent her children to Lithuania for safety before the vote.
Some 6,700 people were arrested in the wake of the election, and many have spoken of torture at the hands of the security services.
Amnesty International said accounts from released detainees suggested “widespread torture”.
What’s the latest with the protests?
Demonstrations have continued following Ms Tikhanovskaya’s call for further peaceful rallies on Friday.
Some 100 staff came out of the state television building to join Saturday’s protests, saying they planned a strike on Monday, AFP news agency reports. Others have signed a letter in support of a strike.
On election day, Belarusian state channels aired the voices of Lukashenko supporters and did not cover the demonstrations. State TV later showed footage of violence to blame protesters and warn people not to participate.
Several journalists have resigned over the coverage.
Earlier on Saturday, thousands of people waved flags, lit candles and laid flowers at the scene close to the metro station where one of the protesters, Alexander Taraikovsky, died on Monday.
Many opposition supporters chanted “Leave!” – a call for President Lukashenko to resign – and some carried signs with slogans against police violence.
The circumstances of Mr Taraikovsky’s death are unclear.
Officials say he died when an explosive device went off in his hand during a protest, but his partner, Elena German, told the Associated Press news agency that she believed the 34-year-old was shot by police.