The police, part of an elite unit, broke down the doors of the Vetevendosje (Self-Determination) party headquarters and arrested founder Albin Kurti and other party members. Hundreds of police in riot gear surrounded the area in the capital, Pristina.
Kurti has been leading opposition to the EU-brokered accord under which ethnic Serbs in the majority-Albanian country will get greater local powers and the possibility of funding from Serbia. He and his supporters also oppose a border demarcation deal with Montenegro.
Kurti has repeatedly released tear gas, and once pepper spray, in parliament to disrupt proceedings. He has been arrested before, triggering riots in Pristina.
Kosovo broke away from Serbia in 1999 when NATO carried out 11 weeks of air strikes to halt the killing and expulsion of ethnic Albanians by Serbian forces trying to crush a guerrilla insurgency.
It declared independence in 2008 and has been recognised by more than 100 countries, including the major Western powers.
Prior to his arrest on Saturday (local time), Kurti addressed several thousand people who gathered in Pristina for a peaceful protest against the accord.
His party said in a statement that police had arrested more than 90 of its members, injuring some of them.
Police said four people including two police officers were hurt in the operation to arrest Kurti, accusing his supporters of attacking officers with chairs, tables and sprays.
