In April, Ukrainian opposition journalist Oles Buzina was shot and killed near his home in Kiev by two masked gunmen. Earlier in the day, the attorney general's office in Kiev said that two suspects had been detained in the Buzina murder case.
"One of the two detainees had served before in Harpoon special unit," Avakov said at a briefing on Thursday.
Later, the minister wrote on Twitter that a third person had been detained on suspicion of organizing Buzina’s killing.
Unhappy with what he considered to be a coup-imposed Ukrainian government, Buzina had advocated for a political settlement to the Ukrainian crisis and the country's federalization.
His murder was preceded by the killings of two other opposition figures, Serhiy Suhobok and Oleh Kalashnikov, also known for their criticism of the current Ukrainian leadership.