Russian President Vladimir Putin says he has formed a police reserve force to intervene in Belarus if necessary, but that point has not yet been reached.
Speaking on Russian state TV, he said Belarus President Alexander Lukashenko “asked me to set up a certain police reserve” and “I have done so”.
“We also agreed that it won’t be used until the situation gets out of control,” he told Rossiya 1TV.
Mr Lukashenko’s disputed 9 August re-election triggered huge protests.
Mr Putin said Russia had an obligation to help Belarus with its security under the two countries’ close alliance, and he stressed the deep cultural, ethnic and linguistic ties between the two nations.
He said the new reserve force would not go into Belarus unless “extremist elements using political slogans as cover cross a certain boundary and start armed robbery, setting fire to cars, houses, banks, try to seize government buildings and so forth”.
The EU and US have rejected the 9 August vote as neither free nor fair. The EU is preparing sanctions against officials it accuses of rigging the result to deliver Mr Lukashenko’s victory and of cracking down on the opposition movement.
The scale of the demonstrations in the Belarusian capital Minsk is unprecedented. Mr Lukashenko claimed a sixth term, after 26 years as president already, with 80% of the vote.
A criminal case has targeted the opposition Co-ordination Council, which Mr Lukashenko accuses of trying to seize power.
The most prominent opposition leader inside Belarus, Maria Kolesnikova, has been questioned by prosecutors. Arriving at the investigative committee building in Minsk, she was applauded as she urged supporters not to give up.
Prosecutors questioned the Nobel literature prize-winner Svetlana Alexievich on Wednesday. She told reporters she had refused to answer their questions, and said the council’s activities were totally legal.
The council was launched by Svetlana Tikhanovskaya, the leading opposition candidate for president, who is now in exile in neighbouring Lithuania.