"The incident took place between 7:00 a.m.to 7: 30 a.m Jakarta time today (Sunday) in Lidwina church", he said. "We need to dig out more details and question the perpetrator", said spokesman Yulianto.
Police are investigating the man's motives, while he is recovering at a hospital.
Prier, who has been living in Indonesia for decades, is now an Indonesian citizen.
They suffered back, neck, and head wounds and are in stable condition.
The policeman who wounded the attacker with two shots to the legs was injured by the man with the Samurai-like sword as the officer intervened to stop the attack, officials said. The reason for the attack Sunday morning was not immediately clear. Then, he burst into the church, allegedly swinging his sword in all directions.
"Everybody started panicking and screaming".
According to reports, the suspect also damaged statues of the Virgin Mary and Jesus Christ, as well as destroyed some books in the church.
A 22-year-old man armed with a sword or machete attacked members of the congregation at St Lidwina Church.
The city, located about 500km south-east of Jakarta, is regarded as the cultural heart of Java, Indonesia's main island.
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.
Indonesia has also seen a resurgence in homegrown radicalism, inspired in part by the militant Islamic State group.
Several children were injured after a man threw Molotov cocktails at a church during a Sunday service in 2016.
Three months later, a church in Samarinda, East Kalimantan, was struck by a homemade bomb which injured four people. It happened when society and government are building harmonization between religious and many elements in the society.