Patna, April 3: National Investigation Agency (NIA) officer Tanzeel Ahmed, who was murdered near Bijnor in Uttar Pradesh in the small hours of Sunday, played an instrumental role in exposing the links of the Indian Mujahideen (IM) in Bihar and Jharkhand.

Tanzeel (45), an assistant commandant of the Border Security Force who was on deputation with the NIA, was killed and his wife seriously injured when two motorbike-borne assailants opened fire at the couple.

Tanzeel, who was with the NIA since 2009, was part of the team assigned to probe the serial bomb blasts in Bodhgaya and Patna's Gandhi Maidan on July 7 and October 27, 2013, respectively. At least six people were killed and 89 others injured in the Patna blasts.

A senior Indian Police Service (IPS) officer who was earlier posted with the NIA recalled that Tanzeel had played a key role in the arrest of Danish (20), said to be a right-hand man of IM co-founder Yasin Bhatkal, from Chakjohra village in Darbhanga on January 22, 2013. Tanzeel had camped for almost for a week in Darbhanga to trace Danish, whose name had also figured in the serial bomb blasts in Pune, Delhi and Bangalore. "A Delhi police team was on the lookout of Danish in connection with the 2010 Jama Masjid blast case," the IPS officer revealed.

He was also involved in the investigation into Bengal's Burdwan blasts of October 2014. An officer at Laheriasarai police station in Darbhanga district described Tanzeel as a brave and competent officer. "I still have fresh memories of the slain officer; he spent hours with us during his visit to Darbhanga to expose the IM's connection in several north Bihar districts including Darbhanga, Samastipur and Madhubani," said the officer, who is not authorised to speak to the media.

Sources in the NIA said Tanzeel had worked under Bihar-cadre IPS officer Vikas Vaibhav when the latter was posted with the NIA on deputation. Vaibhav, who served the NIA from 2011 to 2015,wrote on his Facebook page: "Deeply saddened by the sudden loss of Md. Tanzeel. An asset to the NIA. He will remain in our hearts. My deepest condolences."

Tanzeel had also been engaged in carrying out raids at the suspected hideouts of IM operatives in Ranchi's Sithio area. An NIA source said: "It was Tanzeel who had exposed financial transactions in the bank accounts of Yasin Bhatkal's wife, which led to his arrest."

A senior home ministry official said Tanzeel had been part of the NIA team that busted a nascent Islamic State network in January, leading to the arrest of 17 young men across the country.

"He was also probing the fake currency racket run by the Indian Mujahideen from Pakistan and Bangladesh," the official said.

The Uttar Pradesh police have sealed the borders of Bijnor district and launched a manhunt for the killers. Additional director-general Daljeet Singh Chaudhary said the police's special task force was handling the case but all the senior officers in western Uttar Pradesh, including members of the anti-terrorist squad, were on the spot.