A commission spokeswoman also rejected Minsk's recent offer of deeper economic cooperation with Europe, saying Belarus must first initiate democratic reforms.
The criticism follows the sentencing on September 5 of two activists of the Youth Front (Malady Front) for attending a recent protest rally.
A Belarus court handed down seven-day prison sentences to the man and woman a day after they were detained along with other activists while protesting the trial of fellow Youth Front member Ivan Shyla.
Christiane Hohmann, a spokeswoman for the European Commission, said in Brussels today that the European Union was "dismayed" over the recent course of events.
"We are dismayed at the reports of continued arrests of members of civil society for having asserted their civil and basic rights of expressing themselves," she said. "The repetition of politically motivated arrests which we have observed over the recent months is not an encouraging sign for Belarus's willingness to reengage fully with the European Union."
Hohmann also rejected the offer of deeper economic cooperation, especially in the field of energy transit, made by Belarusian Deputy Foreign Minister Valery Voronetski on September 3 at a European Neighborhood Policy conference in Brussels.
Hohmann said the EU would not let the country's authoritarian leadership "pick and choose" which areas to cooperate in, adding that closer ties are contingent on further democratization in Belarus.
"A rapprochement with the EU requires that Belarus takes convincing steps towards democratization and respect for human rights, including the right of people to express their opinion, and the right of NGOs to exist," she said.
The EU offered Belarus membership in the bloc's European Neighborhood Policy in November 2006, under the provision that Minsk commit itself to democratic reforms.
Today, Hohmann said the authorities' actions in Belarus were "in full contradiction" with the EU's message. She said there were "no encouraging signs" in Minsk.