Rapid Action Battalion (RAB)-4 in a drive arrested six-extortionist from the capital`s Pallabi area on Tuesday.The arrested were identified as Sento Mia, Millon alias Sumon, Yamin Sarker alias Monti, Babu Ahammed alias Babu, Masud Rana alias Rana and Solaiman Kader alias Pavel.A team of RAB-4 conducted the drive in the area and arrested the extortionists, members of Shahadat Bahini(a killer group), the RAB official said while addressing a press briefing.