The demonstration in central Minsk had only just started when riot police in combat gear moved in to grab protesters as a female demonstrator tried to unfurl a poster, a Reuters photographer reported from the scene.
Several opposition protesters had been detained before the rally, which was banned by the authorities.
Riot police targeted photographers and cameramen, trying to damage their equipment. An opposition paper photographer was detained.
Belarus's European Union neighbour Poland on Monday condemned the detention of about 40 ethnic Polish activists, days after Warsaw recalled its envoy in protest over an earlier crackdown.
Belarus President Alexander Lukashenko, who brooks little dissent and has ruled his ex-Soviet nation with an iron hand since 1994, has been wooing the European Union while ties with close ally Russia soured over energy prices and other issues.
Polish Foreign Minister Radoslaw Sikorski on Monday urged Belarus "to return from this bad path" and called on the EU to put pressure on Minsk.
EU foreign policy chief Catherine Ashton said in a statement issued on Tuesday she was "disappointed by the arrests of 40 members of the Union of Poles and other civil society representatives in Belarus".
"The European Union has demonstrated considerable openness to engagement with Belarus," Ashton said.
"The success of this engagement is conditional on steps towards democratisation and upholding human rights, including minority rights, taken by the government of Belarus," she added.
"These developments undermine our efforts to strengthen relations between the European Union and Belarus," Ashton said.
Tensions have periodically erupted between Minsk and Warsaw over Belarus's treatment of its large Polish minority, which numbers some 400,000 people in a country of 10 million.
(EurActiv with Reuters.)
