Calcutta, July 6: The Bengal CID has learnt that Mohammed Masiruddin alias Mosa, arrested from Burdwan on the suspicion of links with the Islamic State, had been in touch with an IS operative believed to be behind the murder of a professor in Bangladesh in April, sources said.

A.F.M. Rezaul Karim Siddique, who taught English at Rajshahi University, had been hacked to death with machetes on his way to work.

The IS had claimed it killed Siddique, 58, because he had "called for atheism" in Bangladesh. Police, however, had said the professor was targeted because he was involved in cultural activities. Siddique had founded a music school and used to edit a literary magazine.

The police had arrested a suspected IS operative, Maskawat Hasan Sakib, for the murder. "It appears that Mosa was in touch with the IS handler who had hired Sakib to murder Siddique," said a CID officer who is part of the team interrogating Mosa.

Mosa, whose cellphone records suggest he was in contact with IS operatives through chat apps, is suspected to have met the handler, whose name central intelligence agencies have not given yet, in Malda last month.

Mosa, who hails from Birbhum's Labhpur, was arrested yesterday by the CID after four hours of questioning. He is suspected to have been in touch with "hardliners" in Bangladesh, Syria and Afghanistan.

Mosa, 25, had been picked up from a train in Burdwan on Tuesday night while on his way to Labhpur from Chennai via Howrah. The CID suspects he had been in contact with Jamaat-ul-Mujahideen Bangladesh (JMB) activists involved in the 2014 "accidental" blasts in Burdwan's Khagragarh.

A 13-inch machete and an improvised firearm with three rounds of ammunition had been seized from Mosa.

Officers interrogating Mosa suspect that the Bangladeshi handler of Sakib had tasked Mosa with beheading a neighbour in Labhpur, raping his daughter and plundering valuables to "prove his mettle to the IS before he could be given bigger assignments".

The officers said the murder and rape would have "helped Mosa prove his worth to the IS". They added that the IS planned to open a "sleeper cell" in Bengal and give Mosa an important role in it if he succeeded in his mission.

The family that Mosa had allegedly zeroed in on has shifted to Calcutta and visits Labhpur occasionally. Two Labhpur youths - Saddam Hossain alias Kalo and Sheikh Abbasuddin alias Amin - had allegedly been hired by Mosa to assist him in the assignment. The duo were arrested today in Birbhum.

Mosa had allegedly contacted Kalo and Amin and told them to wait for him at Ahmedpur railway station in Birbhum on Tuesday. Mosa was supposed to get off the Visva Bharati Fast Passenger train and meet the duo before proceeding towards an undisclosed location.

"Kalo and Amin have been charged with waging war against the nation and conspiracy to wage war. They will be produced in court tomorrow," a senior CID officer said.

Mosa was today remanded in 14 days' police custody by a Howrah court.

A CID team from Bengal today visited Tiruppur district in Tamil Nadu and spoke to Mosa's wife and two children. Mosa ran a grocery shop there.