MINSK (Reuters) – Belarusian President Alexander Lukashenko’s main rival has been detained for questioning in a crackdown on opponents before an Aug. 9 presidential election, lawyers for the detained candidate said on Thursday.

Lukashenko has allowed little dissent in the former Soviet republic since his rule began in 1994 but faces the biggest challenge to his authority in years, with thousands of people taking to the streets to support opposition candidates.

Viktor Babariko, widely seen as Lukashenko’s main challenger in the election, had been taken in for questioning by police, his lawyers said. State television said he was being questioned, without citing a source.

“According to the information we have, his car was stopped and he was delivered for what they call a conversation,” lawyer Alexander Pylchenko told reporters. “Actually this is a detention.”

Babariko’s lawyers were not allowed into the building where he was taken and were not told of his legal status, they said.

“This is a flagrant violation of the constitutional right to defence,” said one of his lawyers, Dmitry Loevsky.

Babariko’s election team said the authorities were also conducting a search at Babariko’s house.

Public frustration with Lukashenko’s handling of the COVID-19 pandemic and grievances about the economy and human rights have reinvigorated opposition to his rule.

Babariko is a former head of the local unit of Russia’s Gazprombank, whose offices were raided in June in a tax evasion and money laundering case. Belgazprombank has been taken into temporary administration and 15 employees have been detained.

Officials at the government’s department for financial investigations were not immediately available for comment.

Another election candidate said this week she was pressing on with her campaign despite receiving a threat to have her children taken away.

Svetlana Tikhanouskaya decided to run after her husband, an anti-Lukashenko blogger, was arrested last month for threatening public order.