Police said the attacker - who was captured by locals after jumping into a nearby river - is a 32-year-old former terror convict from the West Java town of Bogor. TV footage showed the injured man lying on the deck of a motorboat, wearing a black shirt with the word "jihad" written on it.

The suspect was sentenced to three-and-a-half years in prison over an attack in 2011 and was released in July 2014, before moving to East Kalimantan in 2015, National police spokesman Maj. Gen. Boy Rafli Amar said.

The suspected role played by the other four detainees has so far not been made clear.

Two-year-old Ade Intan Marbun died from complications on Monday after suffering burns to over three quarters of her body, East Kalimantan police spokesman Fajar Setiawan said. "It affected her respiratory system and efforts to save her failed and she died early Monday," said Setiawan.

The other children suffered less serious injuries and were still being treated in hospital. "We hope they can come home soon," said Setiawan.

The attack on Sunday took place in the East Kalimantan province on the island of Borneo when a man on a motorbike threw a Molotov cocktail as he rode past Oikumene Church in Samarinda, the provincial capital of East Kalimantan province.

Rising Islamic attacks

Indonesia - traditionally one of the world's more liberal Muslim-majority countries - has seen an uptick in Islamic militancy in 2016, with the country's quasi-secular constitution being questioned in some quarters for first time since 1945. The country is home to substantial populations of Christians, Buddhists and Hindus.

Sunday's attack is the second explosion at a church in Indonesia this year after a would-be suicide bomber failed to detonate a bomb during a Catholic church service in Medan, the provincial capital of North Sumatra, in August. He managed to injure a priest with an ax before being stopped.

Authorities believe IS has more than 1,200 followers in Indonesia and about 400 Indonesians have reportedly joined IS, according to Indonesia's counterterrorism agency, with most traveling to Syria and Iraq. An IS-linked assault in the capital Jakarta in January killed four people, with police saying at the time that the attacker had been imprisoned on terrorism charges in the past and had had links to radical networks.

jbh/msh (Reuters, AP, AFP)