A sword-wielding attacker wounded four churchgoers in the Indonesian city of Yogyakarta yesterday before being shot and wounded by police who said they could not immediately confirm whether it was a terrorism-related incident.

Police said they were investigating possible motives for the attack by the suspect, believed to be a university student, at a Catholic church service in Yogyakarta.

The condition of the wounded people was not immediately clear. Among them was a German-born priest who had been leading the service and who had lived in Indonesia for decades, according to a fellow priest, Dwi Harsanto.

A police officer was also stabbed while trying to detain the suspect.

"We cannot confirm yet if this was a terror-related incident," said Yogyakarta police spokesman Yuliyanto, who goes by one name like many Indonesians. "We can confirm the suspect has been detained and is being treated in hospital."

Indonesia is an officially secular country and has the world's largest population of Muslims, as well as sizeable minorities of Christians, Hindus, and those who adhere to traditional faiths.

Communal and religious tensions have been on the rise in recent years as calls by hardline groups for sharia, or Islamic law, to be implemented nationally grow louder.

Indonesia has also seen a resurgence in homegrown radicalism, inspired in part by the militant Islamic State group.