Abonmai was abducted by a group of alleged rebels of NSCN-IM from Tamenglong on Wednesday and hours later, his bludgeoned body was retrieved 7 km away.
Imphal West SP S Ibomcha Singh said that police arrested the militant from Lairikyengbam Makha Leikai area under the jurisdiction of Lamphel police station of the district on Tuesday.
No one was arrested in this connection as none of the occupants of the house were found during the search operation, the police said.
The duo, both in their 40s, was arrested on Thursday after they took to Facebook to extend their condolences, while also writing that cow dung or cow urine was no cure for COVID-19.
The officer said state force managed to recover one .32 pistol loaded with one live round, by the police.