Indonesian police said yesterday that they had arrested the wife of the suicide bomber who struck at police headquarters in Medan, North Sumatra, a day earlier, killing himself and injuring six others.
National police spokesman Dedi Prasetyo also told reporters in Jakarta that the woman, identified only by her initials D.A, was active on social media and had interacted with a female terrorist imprisoned in Medan about plans to bomb the holiday island of Bali.
"In their social media network, they had planned terrorism attacks in Bali," Brigadier-General Dedi said, referring to the women.
He added that the police believed that D.A. had radicalised her 24-year-old husband, who has so far also been identified only by his initials, R.M.N.
Investigations are continuing into whether R.M.N. was "connected to a structured or non-structured network", the spokesman said.
Based on the probe so far, the suicide bomber was a "lone wolf", or had acted alone.
Three other members of his family were reported to have been detained on Wednesday in Medan, the provincial capital of North Sumatra. It was not clear if they had been released yesterday.
During a raid on R.M.N's house, the police found pipes, bows and arrows.
One local television station, Kompas TV, reported that police also found pipes and explosive materials in another raid on the house of a man, identified as S.A, who was allegedly considered a religious leader by the bomber.
Wednesday's attack took place at around 8.40am local time, 20 minutes after R.M.N. appeared on closed-circuit television walking into the police compound.
North Sumatra police spokesman Tatan Dirsan Atmaja said the bomber, clad in a ride-hailing service jacket, entered the police compound twice. He was cleared after physical checks on the first occasion, but ignored orders to remove his jacket when he returned to the compound.
Intelligence and terrorism expert Stanislaus Riyanta said R.M.N. was most likely affiliated with the Islamic State in Iraq and Syria (ISIS).
He also said that Wednesday's incident should serve as a warning for security forces to be alert for more terror attacks.
"Christmas and New Year can be their favourite time to perform their actions," he said.
In recent years, radicals, some linked to ISIS-inspired militant group Jamaah Ansharut Daulah, have targeted the police and security forces.
The Medan attack came a month after a suspected militant stabbed and wounded former chief security minister Wiranto in Banten.
In August, an alleged militant attacked police officers at a station in Indonesia's second-largest city of Surabaya, but the police managed to arrest him.
The official Antara news agency on Wednesday quoted Indonesia's chief security minister Mahfud MD as saying that the Medan bombing would lead law enforcement agencies to uncover the terrorist network in North Sumatra, just as they did in West Java with the arrest of 51 terror suspects following the knife attack on Mr Wiranto, a former army general.
Professor Mahfud also revealed that one suspect of the Medan attack escaped, local media reported.
Police headquarters in other Indonesian cities, including Denpasar in the country's most popular tourist destination, Bali, and Makassar, the provincial capital of South Sulawesi, have tightened security following the incident in Medan, local media reported.
Safety and security at airports across the sprawling archipelago have also been tightened.
"We will take preventive measures so that a similar incident won't happen again," said Brig-Gen Dedi.