JAKARTA (Reuters) - A sword-wielding attacker who injured at least three churchgoers and a police officer in Indonesia’s Yogyakarta city at the weekend had attempted to travel to Syria and had showed signs of being radicalized, the national police chief said on Monday.

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The attack comes amid heightened concerns over religious tension in the world’s most populous Muslim-majority country, which has also seen a recent resurgence in homegrown militancy.

“There is a strong and concerning indication that he was exposed to radicalism. Radicalism which is pro-violence,” National Police Chief Tito Karnavian told reporters in Jakarta.

Police are currently investigating whether the attacker acted alone or with the help of a larger network.

Authorities estimate there are hundreds of sympathizers of the group Islamic State in the country. Many who traveled to Syria to join the group have returned as it loses territory in the Middle East, and officials believe they could pose a security threat to Southeast Asia.

Four people were killed and 20 injured in 2016 after an Islamic State-linked cell used guns and bombs to mount an attack in the heart of Jakarta’s business district.

There have since been a number of small-scale Islamic State-inspired incidents, including a thwarted suicide attack on the presidential palace last year.

President Joko Widodo said Indonesia had “no place for intolerance”.

“Our constitution guarantees freedom of religion, so we will not give a single place to people who act, grow and spread intolerance in our country...Especially for those who adopt violence,” Widodo said on Monday, when asked about incidents targeting religious minorities.

Indonesia is predominantly Muslim but has sizeable minorities of Christians, Hindus, Buddhists and members of other traditional faith groups.

The church attacker, believed to be a university student, injured at least four people, including a German-born priest and the police official who eventually detained him.

Video footage verified by police showed the church attacker brandishing a long sword, shouting, and lunging at worshippers. Police shot him twice in the leg and he was being treated at a local hospital. They previously said the suspect had been shot in the stomach.