Milinkevich said that even though President Alyaksandr Lukashenka has clamped down on dissidents and students, the demonstrations against his regime will not stop.
Milinkevich was speaking to the European Parliament in Strasbourg on December 11, a day before he was to receive the Sakharov Prize, the EU's top human rights award.
Milinkevich ran unsuccessfully against Lukashenka in a presidential election in March that officials said Lukashenka won overwhelmingly but opposition activists and Western countries rejected as rigged.
Milinkevich spent two weeks in jail following an April 26 protest that attracted about 10,000 people, and was recently briefly detained three times.
Milinkevich said fellow dissident Alyaksandr Kozulin, imprisoned since this spring's protests, remains in critical condition after refusing to end a hunger strike that has lasted more than 50 days.