Belarusian opposition leader Sviatlana Tsikhanouskaya has accused the country’s president Alexander Lukashenko of using political prisoners as “hostages”, as the EU prepares to increase sanctions on his regime.

Lukashenko has been battling to reassert his control over Belarus since his claim of a landslide victory in a flawed election last August triggered the biggest protests in Belarus’s independent history.

About 35,000 Belarusians have been arrested in the ensuing crackdown, with many claiming they have been tortured. Lukashenko has also targeted the media, forcing Belarus’s main independent news portal offline. Last month, he deployed a fighter jet to intercept a Ryanair flight and arrested Roman Protasevich, a dissident who was on board.

In an interview with the Financial Times Tsikhanouskaya described the repression as “Stalin-like”, and the worst that Belarusians had endured since Lukashenko came to power in 1994, three years after the country declared independence from the USSR.

“We could never imagine that the regime could be so cruel. Of course, in the past we had oppression of demonstrations, but we never had so many people [being arrested]. People are really scared. They are frightened to go outside, to live,” the exiled leader said.

“The regime is now collecting as many hostages as possible to trade in exchange for lifting sanctions.”

EU foreign ministers are due to meet on Monday to finalise the latest in a series of sanctions they have imposed on Lukashenko’s regime since last year’s election and the brutal crackdown on dissent that followed.

Diplomats told the FT on Friday that member states had provisionally agreed to target Belarus’s financial, oil, potash and tobacco sectors, which are seen as key sources of foreign currency for the regime.

Tsikhanouskaya said it was important that the measures were rolled out in force. “If the sanctions are imposed step by step, it’s easier for the regime to find ways out,” she said. “But if they are imposed in one go, it’s much more difficult to evade them.”

The latest round of sanctions was triggered by the detention of Protasevich, who infuriated Lukashenko by playing a key role in reporting on and co-ordinating last year’s protests.

Since his arrest, Protasevich — who was seen with apparent bruises on his face and livid marks on his wrists — has been paraded by the regime at a series of recordings and press conferences in which he praised Lukashenko.

Tsikhanouskaya condemned Lukashenko’s actions, saying he was acting out of “hatred” and fear of change in Belarus. She said it was clear Protasevich had been speaking under duress.

“Roman is in danger,” she added. “His task is to survive there. No one can understand — especially people in democratic countries — how people are threatened [in Belarusian prisons]. It’s immoral even to discuss the content of these press conferences or these interviews. We have to discuss how to release him, and that is it.”

Human rights groups say there are now more than 500 political prisoners in Belarus as a result of Lukashenko’s crackdown. Among them is Tsikhanouskaya’s husband Siarhei, who was detained last year, thwarting his plans to run against Lukashenko for the presidency. He is due to face a closed hearing later this week along with several other dissidents, including the blogger, Ihar Losik.

Tsikhanouskaya said it was unclear what would happen at the hearing given the captured nature of Belarus’s judicial system. She renewed her call for the release of all political prisoners, adding that the EU should not relax sanctions before this had been achieved.

“In all my meetings I have urged EU leaders: don’t let the regime trade with political prisoners. Everybody has to be released,” she said. “House arrest is not freedom. Forcing people out of the country is not freedom.”

Tsikhanouskaya said the only way out of Belarus’s political crisis was for a fresh, free and fair vote to be held.

“When everyone is released, it doesn’t mean that our crisis is over. Absolutely not. It is a precondition of getting out of this crisis. But that’s all,” she said. “Then the next stage is dialogue with the regime and new elections . . . New elections — this is the only way out.”