Exiled Belarussian opposition leader Svetlana Tikhanovskaya on Thursday urged democratic governments to make Alexei Navalny's death a "red line" with actions and not just "words of support".
Navalny, an anti-corruption crusader and leading domestic foe of Russian President Vladimir Putin, died last Friday aged 47 in an Arctic prison.
His wife Yulia Navalnaya has accused Putin of having murdered her husband.
"Navalny's death might become a green light or a red line for further murders," Tikhanovskaya told reporters in Vienna ahead of speaking at a meeting by the Organisation for Security and Co-operation in Europe (OSCE).
"If the powerful democratic world limits (itself to) only words of support, empathy, it will give more opportunities for dictators to kill their opponents without any consequences," she added.
Instead, governments should send a "strong signal" in terms of "sanctions or accountability mechanisms" to ensure that "those who kill their opponents, will be brought to justice".
Navalny's "murder personally affects me greatly, because my husband is in the same situation", she added.
Tikhanovskaya's husband Sergei Tikhanovsky is among a number of top opposition leaders still in jail. He was sentenced to 18 years in prison in 2021 convicted of "organising riots and inciting social hatred".
Earlier this week, a Belarusian political activist Igor Lednik jailed for "defamation" against Lukashenko died in prison, his political party said.
Tikhanovskaya said her husband had been held incommunicado since last year.
"(Our) lawyer is not allowed to visit him, letters are not delivered. I don't know in what physical state he is in, if he is in punishment cells or being tortured," she said.
The Belarusian authorities have cracked down on opponents of the country's leader Alexander Lukashenko -- an ally of Putin and in power since 1994 -- after mass protests erupted in the wake of a 2020 presidential election the West says he stole.
The repression means there will be no meaningful opposition at the parliamentary elections on Sunday, the first nationwide ballot since 2020.
Tikhanovskaya dismissed the vote as a "Soviet ritual" and "fake circus" designed to legitimise Lukashenko and his decade-long rule.
"All the media (landscape) is ruined," she told reporters. "All the political opponents are in prison or had to flee Belarus.
"There are no NGOs, no political competition. At most polling stations, there is only one pro-regime person" Belarusians can vote for, she said.
Minsk has been subjected to repeated rounds of sanctions over its clampdown on the opposition and for its role as a staging post in Russia's war on Ukraine.
