"We had information that the group was hatching a plot to carry out violence in the capital Dhaka, (northeastern port city of) Chittagong and (northwestern) Rajshahi," joint commissioner of police Monirul Islam said.
He said the outfit - Harkat-ul-Jihad-al-Islami - had also planned to attack a number of political figures known for their "secular outlook" alongside a number of government offices and infrastructures.
"The four militants were arrested from three different areas of the city overnight when we also raided two of their secret labs where the explosives were manufactured," police said in a press briefing here today.
An official said that one of the suspects was a chemistry student of a private university who was recruited by HuJI for his ability to make bombs while the two laboratories were found at Wari in the old Dhaka and Fatullah at the outskirts of the city.
Police said the outfit was trying to reunite the militant groups under a single banner of "Bangladesh Jihadi Group" as massive security clampdown in recent years had severely weakened the extremist outfits.