DPS says the arrest of three of its mayors is political pressure and an attempt to scare voters.
The party says the raids are linked to its criticism of the government. It says it will keep exposing corruption schemes. It will also appeal to European institutions and judicial bodies over the actions of the police and security services.
The issue also reached the European Parliament in Brussels. Elena Yoncheva, an MEP in the European Conservatives and Reformists group, condemned the arrests. She said such moves days before the presidential vote are unacceptable and may have political aims behind them.
"Detention is not a conviction, and it is unacceptable to carry it out in a humiliating way," Yoncheva said.
She added that detention must not become a public humiliation and a spectacle that frightens the voters of one party.