The elite force arrested Kamrul, who maintains close ties with the Janajuddho faction of outlawed Purba Bangler Communist Party, for suspected role in the attack that killed 19 people and injured over 200 others.

Sources said Rab officials were grilling him in an undisclosed place in Dhaka to find out clues to the crime and operatives who probably carried out the well-orchestrated bombing in the heart of Dhaka.

A source said Rab officials were reeling from the ruling alliance pressure to release Kamrul as he enjoys the backing of two influential legislators -- one from Khulna and the other from Pirojpur.

Sources in Dhaka and Khulna said Kamrul's two younger brothers Shoeb, also known as Ripon, and Sumon alias Babu, are self-styled commanders of the Janajuddho hit men and most trusted confidants of faction boss Tapan.

Kamrul does not have any official link to the outfit, but works secretly for it, they said.

Kamrul and his brothers are accused in multiple criminal cases, including the killing of Havilder Akram on April 10 this year near a powerhouse in Khulna City.

The Tapan faction of Janajuddho claimed responsibility for bombing Akram to death that prompted police to raid the Khulna City house of Moulana Wahab, father of the trio.

Sources said Rab did not admit Kamrul's capture because of the pressure from the two lawmakers.

"Rab might be compelled to release Kamrul anytime for the tremendous pressure before his capture becomes public," a source said.

If Rab can keep Kamrul in their custody without giving in to the political pressure, it will take him to Khulna to arrest other suspects in the outlawed outfit that widely uses grenades in their operations.

Sources said Kamrul maintains good links with intelligence officials and his contacts in a number of countries where he exports manpower.

"The Janajuddho operatives are evading arrest because of his cosy links with intelligence agents,," a source said.

A source said Kamrul was arrested on Baily road in a joint sweep by Rab-1 in Dhaka and a Khulna unit of the force, but could not give details.

But Rab-1 Commanding Officer Lieutenant Colonel Chowdhury Fazlul Bari told The Daily Star that his force did not arrest anyone on the road on Tuesday.

Ramna police could not confirm Kamrul's arrest, but said Rab arrested four people on the road yesterday.