A police team from Boudh arrested the duo, identified as Duryodhana Sahu and Kunti Sahu, from Raikia area of Kandhamal District last night, they said.
Both the accused persons were allegedly involved in another murder case of 2004 wherein the deceased advocate Hemanta Sahu was a prosecution witness, they said.
Two other persons have also been detained by the police at Baunsuni Police Station in Boudh for the purpose of investigation, police said.
Advocate Hemanta Sahu was murdered with sharp weapons on Tuesday by unidentified assailants on a road near his village Bahira of Boudh District.
Lawyers in Boudh have launched a cease work agitation protesting the incident and demanding speedy investigation into the murder and arrest of culprits.