Security personnel inspect the interior of St Sebastian’s Church in Negombo on April 22, 2019, a day after the church was hit in series of bomb blasts targeting churches and luxury hotels in Sri Lanka./ AFP

The Sri Lankan government believes a local Islamist extremist group called the National Thowheeth Jama’ath (NTJ) was behind the deadly suicide bomb attacks that killed nearly 300 people, government spokesman Rajitha Senaratne said Monday.

Senaratne, who is also a cabinet minister, added that the government was investigating whether the group had “international support”.

Documents seen by AFP show Sri Lanka’s police chief issued a warning on April 11, saying that a “foreign intelligence agency” had reported NTJ was planning attacks on churches and the Indian high commission.

Not much is known about the NTJ, a radical Muslim group that has been linked to the vandalising of Buddhist statues.

A police source told AFP that all 24 people in custody in connection with the attacks belong to an “extremist” group, but did not specify further.