After a series of raids following a suicide attack outside a cathedral on the first day of the Easter Holy Week, Indonesian police found powerful explosives and detained more alleged Islamist extremists on Monday. The Jakarta police department refused to comment on the raids, and the national police department did not respond to a request for comment.

The two bombers were the only people killed in Sunday’s attack in Makassar, Sulawesi, which injured 19 people and occurred as mass was finishing. The bombers were a married couple who belonged to Jamaah Ansharut Daulah (JAD), an Islamic State-inspired organisation accused of carrying out suicide attacks on churches and police stations in Surabaya in 2018, killing at least 30 people.

National Police spokesperson Argo Yuwono said the couple had been married for six months and that police were investigating their Makassar home. L and his partner, YSF, were only known by their initials. The couple’s neighbours named the man as Lukman and his wife as Dewi, and said they were between the ages of 23 and 26.

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Listyo Sigit Prabowo, the national police chief, said 13 people had been detained in Greater Jakarta, West Nusa Tenggara, and Makassar after the attack and played various roles in its execution, from making explosives to detonating them.

The raids yielded 5.5 kg (12.13 lb) of explosives and a number of chemicals, including triacetone triperoxide (TATP), a strong yet unreliable mixture often used by Islamist militant groups, according to Listyo. At a press conference, Listyo said the male bomber wrote a letter to his family expressing his desire to die for his beliefs.