By Andrei Makhovsky
MINSK (Reuters) - Thousands of opposition supporters clapped, cheered and chanted at a rally in Minsk on Thursday evening, defying a crackdown by Belarus President Alexander Lukashenko's government ahead of a presidential election this weekend.
Lukashenko, a 65-year-old former Soviet collective farm manager, is facing the biggest challenge in years to his rule and accuses protesters of being in cahoots with foreign backers to destabilise the country.
Protests have swelled in support of his main challenger Svetlana Tikhanouskaya, a former English teacher who launched her bid after her husband, who planned to run, was jailed.
Her campaign was forbidden from staging a planned rally on Thursday evening, so her supporters gathered at a government-sanctioned outdoor concert at a separate venue.
Riot police arrested DJs after they played a song called "Changes" favoured by the opposition.
"This is an amazing atmosphere, amazing people, I want to be with them. And I want changes," said Irina, a 47-year-old teacher who gave only her first name.
Lukashenko earlier announced that a number of U.S. nationals had been detained but did not say when or why.
Belarus has sought to mend fences with Washington as ties fray with traditional ally Moscow, and in February hosted Secretary of State Mike Pompeo, the most senior U.S. official to visit in more than two decades.
"Some people were detained with American passports, married to Americans, working in the State Department," the Belta news agency quoted Lukashenko as saying.
The U.S. embassy in the capital Minsk did not reply to a request for comment.
Belarus and Russia also traded barbs again over a group of suspected Russian mercenaries who were detained in Belarus in July and accused of plotting to foment unrest.
Russia has said the men were employees of a private security firm and were passing through Belarus on their way to Latin America. Russia's foreign ministry spokeswoman said the men should be returned to Russia.
Lukashenko said they had broken the law.
"A hybrid war is going on against Belarus and we should expect dirty tricks from any side," he said.