Bangladesh's elite security force Tuesday arrested three suspected Islamist militants, including a British citizen who police said was the "main planner" of the murders of two prominent atheist bloggers.

Rapid Action Battalion (RAB) spokesmen said they had arrested Touhidur Rahman, 58, and two other "active members" of Ansarullah Bangla Team, which was banned in May over a spate of killings of bloggers.

"We've arrested them in the capital today. We can confirm that Rahman is a Bangladesh-origin British citizen. He is the main planner of the attacks on Avijit Roy and Ananta Bijoy Das," Major Maksudul Alam of the RAB told AFP.

"He told us that he is a British citizen," Mufti Mahmood, the head of the RAB's legal and media division, told AFP, adding that the three would be paraded before the press later Tuesday.

Four secular bloggers have been hacked to death in Bangladesh since the start of the year, including Roy and Das.

Roy, a US citizen who was born in Bangladesh, was murdered in February by a gang wielding machetes in an attack in Dhaka.

Das, 33, was killed in similar fashion as he headed to work at a bank in the northeastern city of Sylhet on May 13.