British citizen Hamdan was nabbed from the capital's Kamalapur on Monday morning. He was taken to court which gave police three days for interrogation.
Detective Police Joint Commissioner Monirul Islam told a press conference later in the day that they had found Hamdan by interrogating two suspected Ansarullah Bangla Team members arrested last week.
Asif Adnan, 26, and Md Fazle Elahi Tanzil, 24, were allegedly trying to go to Syria to join the Islamic State militants.
“In primary interrogation, Hamdan admitted that he was recruiting for IS and al-Nusra Brigade.”
According to police, the man worked for al-Nusra from September to December in Syria. He went there from the UK with a friend, via Turkey. Later he worked as a recruiter for some time in Morocco.
The Sunni insurgent group Islamic State was active in Iraq and Syria since 2004, but rose rapidly to prominence this year with its capture of vast swaths of territories.
They have declared a Khilafat in the captured area. The al-Nusra Front is affiliated with al Qaeda.
Monirul Islam said Adnan and Tanzil were drawn to al Qaeda chief Ayman al-Zawahiri’s message of forming an Indian branch.
“In remand they gave interesting information about al Qaeda in Indian Subcontinent. Hamdan was arrested based on their information. He wanted to recruit militants here to create an international network of al Qaeda,” he said.
“They wanted to carry out subversive activities to establish Islamic rule. Police have collected some of their messages,” Islam said.
Hamdan contacted potential recruits through comments on a Peace TV anchor’s Facebook fan page.
IS has over 31,000 fighters, of whom over half come from 80 different countries. The European Union has said at least 3,000 Europeans are fighting for IS.
At court, Hamdan was not represented by a lawyer. He told reporters there that he was caught from Nabiganj in Habiganj five days ago.