Members of Rapid Action Battalion (RAB) detained the prime accused in the case over the killing of newly-elected UP member Abdur Rauf from Boda upazila in Panchagarh district on Sunday.
The detainee is Arif Mia.
Tipped off, a team of Rab-13 conducted a drive in the area and detained Arif from Panchagarh district.
Earlier, on Friday night, Abdur Rauf, a newly elected member of Laxmipur union parishad, was killed by a youth in Gobindapur village of Gaibandha Sadar upazila.
Police claimed to have arrested a man, identified as Rezaul, in connection with the murder.
Touhidul Islam, superintendent of Gaibandha Police, said "A complaint was lodged with Sadar Police on Saturday and the attacker might have killed him over previous enmity."
Local people on Saturday blocked Gaibandha-Sundarganj road at Laxmipur Bazar in Sadar upazila demanding exemplary punishment of the killer.