Police said the accused arrested last night could have hacked the Facebook account of a Hindu youth and posted images of Hindu gods over those of Muslim holy shrines to instigate violence.
"We arrested him last night from the (Brahmanbaria) town. He was on the run and we believe he is one of the main culprits," police official Mizanur Rahman told PTI on phone.
He said 30-year-old Jahangir Alam, a cyber cafe owner, was arrested as police investigations confirmed his crucial role in the mobilising Islamists to carry out the attacks while "we are now trying to be certain if he himself had hacked the Hindu youth's Facebook account".
The district police chief's comments came as a court ordered Alam to be interrogated in custody for four days as he was brought before a magistrate.
Officials said Alam was the last among the detained suspects while police earlier arrested over 100 people for their alleged involvement in Nasirnagar attacks when the Islamists carried out two subsequent attacks ravaging nearly a dozen temples and over 20 houses.