Alyaksandr Kazulin and Mikhail Trepashkin join others, including the Dalai Lama and Zimbabwe's Prime Minister-designate Morgan Tsvangirai, in the running for this year's Sakharov Prize for Freedom of Thought.
Now in its 20th year, the prize, named for the former Soviet dissident Andrei Sakharov, is awarded annually by the European Parliament to individuals or organizations for their efforts on behalf of human rights and fundamental freedoms.
Previous winners include another prominent Belarusian opposition leader, Alyaksandr Milinkevich, in 2006, and the United Nations in 2003.
The eight names will be whittled down to a shortlist of three on September 22, with the winner announced in mid-October.
Kazulin unsuccessfully challenged Alyaksandr Lukashenka in Belarus's 2006 presidential election. He was convicted of hooliganism and inciting mass disorder following clashes between police and demonstrators protesting what they -- and Western leaders -- said was Lukashenka's rigged reelection.
Kazulin always denied the charges and was described by Amnesty International as a prisoner of conscience. He was released last month midway through a 5 1/2-year prison sentence and said he would return to politics.
Trepashkin, the former KGB agent, was released in November 2007 after spending four years in jail for divulging state secrets. (Read an interview with him in Russian here.)
Trepashkin claimed he was framed to prevent him from exposing what he believed was evidence of involvement by the Russian security service, the FSB, in a spate of apartment bombings in 1999.
The bombings, which killed nearly 300 people, were blamed on Chechen separatists and were part of then-Prime Minister Vladimir Putin's reason for sending troops back into Chechnya.
Trepashkin also figured as a potential witness in a more recent murky affair -- the 2006 radiation poisoning death of former colleague Aleksandr Litvinenko.
Trepashkin said he had warned Litvinenko several years earlier that his life was in danger, and after his death released a letter saying Litvinenko's name was on an FSB list of people to be assassinated.