The police have picked up around a dozen suspects for interrogation in the murder of a station house officer and injuries to a constable during a gun battle in Salarpur diara (riverine area) in the early hours of Saturday.

Ashish Kumar Singh, 32, the in-charge of Pasraha police station, was killed and constable Durgesh injured in the gun battle with criminals on the Khagaria-Naugachhia border.

Deputy inspector-general (Munger) Jitendra Mishra, who is leading the joint operation against gangs operating in the diara areas, on Sunday said some close associates of Dinesh Muni and Ashok Mandal have been detained. “We have got evidences of one of the two ganglords being injured in the Saturday attack,” Mishra told The Telegraph.

A joint team of Khagaria, Naugachhia and Begusarai police has been engaged in the combing operation launched on the directive of additional director-general (law and order) Alok Raj. Two quick response teams, two special task force and five deputy superintendents of police have been sent to Khagaria to assist the district police in arresting the cop killers.

“The operation will continue till the criminals involved in the attack on the police are arrested,” Alok said, adding that forensic experts on Sunday collected blood samples from the site of the gun battle.

Police records show that at least 10 cases of murder, crop loot, extortion and Arms Act are pending in Khagaria against Dinesh, a resident of Ajgaiba village under Chausa police station in Madhepura district.

Alok said Pasraha police had left for the diara following a tip-off that active members of Dinesh and Ashok’s gangs had gathered there. But the criminals, hiding in a hut, opened fire on seeing the police. The police retaliated, killing one criminal and injuring another. Only one of the bodies were, however, recovered.

Homeguard jawan Subodh Kumar Yadav, who was part of the raid team, told senior officers that a criminal fired at Ashish from close range when the station house officer went into the hut to find if anyone was injured or killed inside.

Ashish died after being shot in the abdomen and chest.