(HAMBURG, Germany) — Multiple people were shot, some fatally, at a church in Germany Thursday night, police said.

Several people were seriously injured in the shooting, which occurred in a church in Hamburg, police said.

Police said the building where the shooting occurred was being used by Jehovah’s Witnesses.

The incident occurred around 9 p.m. and involved one or more unknown perpetrators, according to an alert from the city of Hamburg.

The streets around the church have been cordoned off and residents have been advised to avoid the area and shelter in place “for the time being,” the alert said.

Hamburg Mayor Peter Tschentscher called reports of the shooting “shocking” and offered his “deepest condolences” to the families of the victims.

“The emergency services are working flat out to track down the perpetrators and clarify the background,” he said in a statement.

ABC News’ Will Gretsky contributed to this report.

This is a developing story. Please check back for updates.

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