DHAKA, Bangladesh — Twelve men suspected of membership in Al Qaeda’s branch in the Indian subcontinent have been arrested in three separate raids in the capital, Dhaka, an elite police unit said on Thursday.

The raids, which began on Wednesday morning and lasted past midnight, were based on internal intelligence reports and preliminary interrogations of the suspects, said Cmdr. Mufti Mahmud Khan, a spokesman for the elite unit, the Rapid Action Battalion. One of the men arrested, Mainul Islam, is a chief coordinator for the group in Bangladesh, he said, and another, Zafar Amin, is an adviser.

Commander Khan said the men arrested had been “inspired” to affiliate with the Qaeda branch after the worldwide leader of Al Qaeda, Ayman al-Zawahri, announced the branch’s existence last September in a video posted on jihadist forums online. In May, the leader of the branch, Qaedat al-Jihad in the Indian Subcontinent, claimed responsibility for the murders of two bloggers critical of extremism in Bangladesh, including a Bangladeshi-American, Avijit Roy, who was killed in Dhaka in February by men with machetes as he was leaving a book fair with his wife.

Five suspects, including Mr. Islam and Mr. Amin, were arrested at a river terminal in Dhaka, where they were arriving by ferry from a district in the country’s south, Commander Khan said. Interrogations led the security forces to a rail terminal near the Dhaka airport, where they arrested five more men. Finally, early Thursday, the forces raided a rented house in the Mirpur area of the capital, where they arrested two more men suspected of membership in the group.