The accused were arrested by three special squads constituted under the supervision of Deputy Commissioner of Police (South Division) H S Revanna, city police commissioner Jyothiprakash Mirji told reporters.
Mirji said the RTI activist Lingaraju and a whistleblower were hacked to death on November 20 at Vittal Nagar in Chamarajpet by the accused in front of his house.
The activist, Mirji said, was hacked to death after he had filed a private complaint in the Lokayukta Court recently against Govindraju, husband of Azadnagar corporator Gowramma. He had also lodged a complaint with the Upalokayukta against the couple.
On November 9, the Lokayuukta police had raided Gowramma and Govindraju's residence and recovered property worth over Rs 16 crore.
Lingaraju is also reported to have provided crucial documents, during preliminary investigation of the cases involving Gowramma and Govindraju, which subsequently led to the raids, according to police.
Treating press reports about the killing of Lingaraju as suo motu PIL, Karnataka High Court had yesterday ordered issue of notice to the officials of the city and state police.