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.