Belarus is seeking the extradition of Svetlana Tikhanovskaya, the opposition figure who challenged President Alexander Lukashenko in last year's disputed presidential vote and fled for her safety.
Ms Tikhanovskaya was forced to escape to Lithuania after she said she received threats to her children amid a violent crackdown on protests.
The Belarus General Prosecutor's Office said in a statement on Friday that Ms Tikhanovskaya faces “prosecution for crimes against the governing order, public safety and the state”.
It added that they had asked Lithuania to return her.
“Everyone who has found refuge in Lithuania can feel safe that they will not be handed over,” Lithuanian Foreign Minister Gabrielius Landsbergis responded in a statement.
“Hell will freeze over before we begin to consider your request to extradite Tikhanovskaya,” he said.
The protests against Mr Lukashenko have continued throughout the freezing winter months.
At the end of February, when Mr Lukashenko was meeting with his Russian counterpart Vladimir Putin, Ms Tikhanovskaya called for new mass protests on March 25.
"I call on all the Belarusians to begin getting ready for that day now – to mobilise the protest spirit, create safety groups, to plan returning to the streets of your cities," she said in a post on her Telegram channel on Feb 22.
“Because the only force that can prevent our country's being sold out is the Belarusian people.”
Hundreds of thousands of people took to the streets in August after Mr Lukashenko, who has ruled the former Soviet nation with an iron fist for 26 years, claimed a landslide victory in a disputed election.
Independent observers believe Ms Tikhanovskaya was the actual winner, but with the ballot papers allegedly burnt by the Central Election Commission, the results are difficult to verify.
The opposition has been calling for new elections to be held.
The European Union, among other countries, have refused to recognise Mr Lukashenko as the legitimate leader of Belarus, imposing sanctions as a response to the crackdown on protesters.
Journalists and rights defenders are facing lawsuits, which have been condemned by international advocacy groups.