The defence ministry in Minsk on Sunday said just under 9,000 Russian troops would be stationed in Belarus as part of a "regional grouping" of forces to protect its borders.
"The first troop trains with Russian servicemen who are part of the (regional grouping) began to arrive in Belarus," Valeriy Revenko, head of the defence ministry's international military cooperation department, wrote on Twitter. "The relocation will take several days.
"The total number will be a little less than 9,000 people."
More information would be provided at a briefing for military attachés, he added.
Belarusian President Alexander Lukashenko said last week that his troops would deploy with Russian forces near the Ukrainian border, citing what he said were threats from Ukraine and the West.
(Reporting by Reuters; editing by John Stonestreet)
