Judicial Magistrate Abdullah Al Mamun passed the order after police produced the Shahjadpur municipality mayor in his court.
Police would seek seven-day remand for interrogating Miru in custody, said Shahjadpur police's Inspector Monirul Islam.
Sirajganj police arrested Miru from Dhaka on Sunday night in a case started over the death of journalist Abdul Hakim Shimul.
Shimul, Shahjadpur correspondent for Bangla daily 'Dainik Samakal', was shot in the eye during a skirmish between two factions of the ruling party's Sirajganj unit on Thursday.
He died at the hospital the next day.
Police said the bullet was fired from Miru's shotgun.
Shimul's wife initiated a murder case against 18 identified and 20-25 unidentified people after the incident.
A large number of people thronged the court premises on Monday. Additional police were deployed to control the crowd.
On Thursday, the clash erupted following 'assault' of Bijoy Mahmud, president of Awami League's student wing Chhatra League at Shahjadpur Government College.
One of the factions encircled Miru's residence, blaming him for the assault on the Chhatra League leader.
Additional Superintendent of Police Abul Hasnat said police did reach the spot right on time but the mayor opened fire despite being told not to do so.
The bullet entered Shimul's skull after piercing one of his eyes, doctors said.
Police have detained eight people so far in the case and have seized the shotgun of the mayor.
Shahjadpur unit of the Awami League has called for expulsion of Miru from the party.