He planned to travel to India and take charge of the JMB wing of the neighboring country.
For this purpose, Rezaul Haque alias Reza, 37, had long been trying to arrange a passport and last attempted in 2020.
Ameer of the mainstream JMB Salahuddin Ahmed alias Salehin, who is now in India and operating outfit activities, instructed Reza to visit the country and take charge.
Salehin went into hiding and take shelter in the country after he was snatched from a prison van in February 2014.
Salehin asked Reza to hand over the charge and go to India as his identity was revealed and he became familiar to many people.
Reza disclosed the plan of the banned militant outfit after the Bomb Disposal Unit (BDU) of the Counter-Terrorism and Transnational Crime (CTTC) interrogated him.
The BDU team arrested Reza from the capital's Badda area yesterday evening, Rahmatullah Chowdhury, additional deputy commissioner of CTTC unit, told The Daily Star.
Reza was in charge of JMB's activities in Bangladesh, and also the chief of recruitment and financial wing of the outfit.
He was arrested in 2005 for his involvement with the countrywide series of the bomb attack and he was behind the bar until he managed to secure bail in 2017.
Besides the series bomb attack, Reza was wanted in three other cases filed with Vatara, Airport, and Government Railway police stations, according to officials.
Salehin handed over the responsibility of JMB's Bangladesh chapter after the senior JMB leader Khorshed Alam alias Salim alias Master was killed in a "gunfight" with police in Bogura on November 6, 2018.
Since then, Reza had smooth communication with the outfit Ameer Salehin through the secret application until the arrest, said Rahmatullah, also the chief of BDU.
During primary interrogation, Reza told investigators that Salehin never got the scope to visit Bangladesh after he went into hiding in India in 2014.
Since then, the Indian part of JMB was used as a "safe house" for the outfit and dozens of leaders often take shelter there, according to sources.
Recently, Salehin got separated from JMB members in India due to the vigilance of the law enforcement agency and started living isolated, for which reason, Reza was invited to visit the country and take the charge there, said a top official of the CTTC unit, requesting anonymity.
The official, however, refused to disclose Salehin's present location.
Asked why Reza was asked to visit India with a passport, the official said he wanted to do some other job after going to the country so that no one could suspect their movement.
"We have some details of JMB activities in India and movement of the Salehin and we would knock the Indian authority soon through proper channel," the official told this newspaper.
In the last two years, Reza allegedly managed to gather around a hundred members for the outfit.
Besides, Reza was also responsible to collect funds for the outfit.
Investigators claimed that they have detected a person in Saudi Arabia, who is working as the financier and sending money for the outfit.
"We are now trying to detect the financial channels and collect personal details of the financier to take lawful action," said another official of the CTTC unit, wishing not to be named.
Only in the month of Ramadan, the outfit fund collection reached Tk 20 to Tk 30 lakh, the official said, adding, this fund was gathered from different local sources in Bangladesh.
BDU Chief Rahmatullah said they would interrogate Reza after taking him on remand to verify some clues and financial issues related to the outfit and then further action will be taken.