Published : 13 Nov 2016, 02:30 AM
Detective Branch arrested the suspect, identified as Khairul Islam alias Jamil, 26, from Kamlapur Railway Station area Friday midnight, DB Joint Commissioner Abdul Baten told reporters at a press conference on Saturday.
He said in the initial interrogation Khairul admitted that he had been involved in both the killings- Niloy and Dipan.
"Khairul followed them regularly and sent information to the organisation's military wing," Baten said at the press conference at DMP's media centre.
He said sacked army major Ziaul Haque, the alleged chief of ABT's military wing, ordered the murders of Niloy and Dipan.
Khairul helped make the plans and execute the murders, the detective said.
"He met Zia for the last time on Sep 26. He joined ABT after Zia did," he added.

On Aug 7, assailants barged into the home of blogger and online activist Niloy at the capital's Gorhan and hacked him to death with sharp weapons.
Around three weeks later, on Aug 31, publisher Faisal Arefin Dipan was found murdered in a similar way in his office at the Aziz Supermarket in Dhaka.
Since February 2015 when writer-blogger Avijit Roy was murdered on Dhaka University campus, several secular writers and bloggers have been targeted and killed. Police said that banned Islamist outfit Ansarullah Bangla Team was behind the killings.
Its chief Jasimuddin Rahmani is serving a prison term after being convicted for the 2013 murder of Ganajagaran Mancha activist and blogger Ahmed Rajib Haider.