Ahmed Azwad Imtiaz Talukder alias Omi, one of the two people detained for attacking police in Comilla, had stayed at a militant hideout in Narayanganj, where Gulshan attack mastermind Tamim Ahmed Chowdhury was living as well, said police.
Omi had left the hideout just seven days before the August 27 operation that left Tamim and two other militants dead.
Even, he also knew the five militants who attacked Holey Artisan Bakery on July 1, police said, adding, Omi was preparing for sabotage under a top leader of New JMB, Moinul Islam Musa, now on the run.
Police claimed that Omi revealed the information in primary interrogation after he was arrested along with Mahmudul Hasan following Tuesday's attack on a patrol team of highway police in Chandina, Comilla.
Omi, an A level student in Dhaka, had left his home back on February 29 last year and since then he was unaccounted for, police said.
OC Nasiruddin Mridha of Chandina police said they were quizzing Mahmudul who was already on a seven-day remand, while Omi with bullets injuries was being treated at a local hospital under police custody.
Acting on their information, police raided a militant den on Wednesday night, seizing a a massive cache of bombs and bomb-making material.
“Omi divulged some important information,” he claimed.
Omi said that he had become radicalised through Twitter and expressed allegiance to Abu Ibrahim Al-Hanif, the chief of Bangladeshi supporters of Islamic State.
Afterwards, Omi left his home for hijrat (migration) and quickly came in touch with Tamim, the military commander of New JMB, said sources in the Counter-Terrorism and Transitional Crime (CTTC) unit of Dhaka Metropolitan Police.
Omi, as the sources said, used to translate the outfit's organisational documents into both Bangla and English. Ahead of the Narayangan raid, he shifted to another such a den in Dhaka and finally moved to Chittagong two months ago.
The CTTC said the duo were carrying some explosives for someone, but it did not mention the identify of the person for the sake of investigation.
Omi and Hasan had rented some flats in Dhaka, where they used to frequent at times, the investigators said.
He also told the investigators that they had many other militant dens in Chittagong, but did not know the location of all of those because they were not allowed to visit another hideout belonging to the same militant group.
However, the militants had been using the Mirsarai hideout as a training centre and bomb-manufacturing factory, police said, where the CTTC unit, after an overnight drive, on Wednesday discovered at least 29 live handmade grenades and 280 packets of splinters, 40 packets of explosive gel, machetes and 11kg bomb-making materials.