Valery Tsepkalo, a former ambassador to the United States and founder of a successful hi-tech park, had been widely seen as President Alexander Lukashenko's top rival in the Aug. 9 vote but he was denied a spot on the ballot last week.
Lukashenko, 65, has run Belarus with an iron fist for a quarter century, relentlessly suppressing free speech in the ex-Soviet country of 9.5 million and cracking down on political opposition.
Tsepkalo told reporters on Friday that he moved to Russia with his two children after unnamed sources in the Belarus's Interior Ministry and the State Security Committee (the KGB) warned him about a looming arrest and plans to strip him of his parental rights and take his children away.
“An order has been given to arrest me,” Tsepkalo said. “Prosecutor's office agents came to (my) children's school and started asking teachers and administrators to sign some kind of papers.”
Authorities in Belarus have not yet commented on his allegations.
Tsepkalo's wife, Veronika, stayed in Belarus and continued to campaign, joining forces with Svetlana Tikhanovskaya, the only opposition candidate allowed on the ballot.
Tikhanovskaya, the wife of jailed popular opposition blogger Sergei Tikhanovsky, earlier this week also said she took her children to an EU country after she received threats in connection with her campaign.
Another opposition challenger for Lukahsenko, Victor Babariko, was arrested last month on alleged money-laundering charges.
The presidential campaign this year has sparked unrest in Belarus amid the coronavirus outbreak and a weakening economy that largely depends on cheap Russian oil and gas. Authorities’ decision not to impose a lockdown during the pandemic,and the government's crackdown on opposition candidates has elicited outrage and prompted protests.
Human rights advocates say more than 1,000 activists have been detained during the protests.
The World Bank has forecast that the Belarusian economy will shrink at least 4% this year, the largest decline in a quarter-century.
Tsepkalo said Friday he plans to return to the country after the election.
“Everything will depend on the outcome (of the vote), but if things heat up in Belarus, I will come back earlier than Aug. 9,” he said.
Lukashenko on Friday alleged that his opponents may resort to hiring mercenaries abroad to fuel unrest at home. He offered no proof for the claims.