The local Detective Branch chief Ohed-uz-Zaman said that they were arrested early on Saturday from a house at the town’s Masumpur.
Crude bombs, bomb-making materials and jihadi literature have been found in their possession, said the Detective Branch OC.
The four have been identified as Nadia Tabassum Rani, 30, Habiba Aktar Ruma, 22, Rumana Aktar Ruma, 21, and Ruma Khatun, 19.
“Six crude bombs, detonators and other bomb-making materials as well as jihadi books have been found in the house,” said the police officer.
He said they suspect them to be involved with the banned militant outfit JMB.
They are being questioned at the office of Sirajganj’s superintendent of police (SP).
The four rented the house in May and have been planning for a major attack, claimed SP Mirazuddin Ahmed.