There territory was in the Bay of Bengal, adjacent to Barguna, Patharghata and Patuakhali districts. They used to conduct robbery in fishing boats. At times, they would abduct anglers and collect ransom from their families.

They did this relatively risk-free. From their Narayanganj safehome, they asked for the money to be transferred over mobile financial services (MFS).

All of this came to light after Rapid Action Battalion (Rab) arrested one of the robbers' fund collectors, Elias Hossain Mridha (28), from Rupganj in Narayanganj on Tuesday night. Rab also seized around Tk five lakh from his possession.

Addressing a briefing yesterday, Khandaker Al Moin, director of legal and media wing of Rab, said Elias controlled the financial transaction network from Narayanganj.

Recently, Elias had received Tk 7 lakh on behalf of the gang's leader, the Rab official said.

Khandaker Al Moin said anglers from Pirojpur, Patuakhali and Barguna districts go to the deep sea in mid-November to catch fish.

His arrest came after abducting seven anglers from the bay, within 30-35km from the coast of Patharghata and Barguna districts. On information, a Rab-8 team patrolled with a helicopter to rescue the anglers.

"Due to Rab's movement, on November 23, the robbers left the anglers on a boat and fled away," claimed the media wing director.

Rab later identified their footprints in Narayanganj and traced their MFS activities to reach Elias. Officials said the robber group has around 15 to 16 members who used to conduct robbery being divided into several small groups.