The wife of an Indonesian militant arrested on Tuesday blew herself and her 21/2-year-old child up early yesterday at their home in Sibolga, North Sumatra, while under siege by the police.

"A team from the Detachment 88 anti-terror squad and local community leaders in Sibolga had spent 10 hours trying to persuade her to surrender. We made a strong appeal, stressing minors were involved," said national police spokesman Dedi Prasetyo.

Police had arrested the woman's husband, Husain alias Abu Hamzah, about 200m from his home the day before. Another militant had been nabbed in a raid in Lampung, southern Sumatra, over the weekend.

Both men, believed to be members of the Islamic State in Iraq and Syria (ISIS) militant group, had planned to launch attacks on the police, among others.

National police chief Tito Karnavian said that two more people were arrested in Sibolga, in addition to Husain.

"In the Lampung raid, we found bombs similar to those we found in Sibolga," Brigadier-General Dedi said, disclosing that materials used to make bombs were uncovered.

"There are possibly still more bombs under the rubble. Police have so far detonated several devices using a remotely controlled robot, and Husain, during the interrogation, said he made many bombs," Brig-Gen Dedi said yesterday.

A police officer who was trying, along with an uncle of Husain, to persuade the militant's wife to surrender, was injured slightly after the woman lobbed a bomb in their direction. The uncle was badly injured later when the woman detonated another bomb in the house.

Neighbours living in a 100m radius from Husain's house in the densely populated residential area have been evacuated, said Brig-Gen Dedi. He added that the blast damaged several other houses in the vicinity.

Indonesian police began a major crackdown on militant networks early last year ahead of the Asian Games in Jakarta and Palembang, South Sumatra, in August and September as well as the International Monetary Fund and World Bank annual meetings in Bali in October.

Figures show that Detachment 88 forces killed or detained 396 militants last year, a record number and a sharp jump from the 176 in 2017. Twenty-five suspects were gunned down during raids last year as they resisted arrest, nine more than in 2017.

Indonesia, which has the world's largest Muslim population, has long struggled with Islamic militancy.

A gun and suicide bomb attack in Jakarta in January 2016 left four attackers and four civilians dead. It was the first assault claimed by ISIS in South-east Asia.

Indonesia suffered its worst terrorist attack in 2002, when the bombings of two nightclubs on the resort island of Bali killed 202 people, mostly foreign tourists.

In May last year, a family of six carried out suicide bombings at three churches in Surabaya, East Java, during Sunday mass, killing 13 people. Two brothers, aged 17 and 15, carried out the first bombing, while their mother, armed with a belt bomb, carried out the second. She was accompanied by her two daughters, aged nine and 12. It was the first-ever suicide bombing by a woman in Indonesia.

Their father, who was in a car, staged the third bombing.

Last May, Presidential Chief of Staff Moeldoko said that nearly 1,500 Indonesians - including women and children - had either tried to go or had gone to the Middle East to fight for ISIS.

Mr Moeldoko, a retired four-star general and former armed forces chief, said that 590 of them were still in Syria or Iraq, while as many as 86 had returned home.