At least six people were killed in a shooting in a Jehovah's Witnesses church in the German city of Hamburg on Thursday, with the gunman believed to be among the dead found in the building, German police said, according to the AFP news agency.
Shots rang out at the church in the Grossborstel area, with the first emergency made at around 20:15 GMT, a police spokesman at the scene said.
"Several people were seriously injured, some even fatally," police said on Twitter.
"At the moment there is no reliable information on the motive of the crime," they added, urging people not to speculate.
Police alerted people to an "extreme danger" in the area using a catastrophe warning app.
Residents must stay indoors and avoid the area, police said, adding that streets surrounding the church have been cordoned off.
Officers were able to access the site quickly after distress calls came in, a spokesman said. The first police at the scene found several lifeless bodies and seriously wounded people.
They also heard a shot in the "upper part of the building" before finding a person in the area where it rang out.
"We have no indications of a perpetrator on the run," said the police spokesman.
Instead officers have "indications that a perpetrator may have been in the building and may be even among the dead."
No details were immediately available regarding the background to the incident and it remains unclear whether the incident was terror-related, though Germany has been hit by several terrorist attacks in recent years.
The worst such attack took place in December of 2016, when Tunisian terrorist Anis Amri killed 12 people and injured dozens more when he drove a truck into a Christmas market in Berlin.
In 2019, a neo-Nazi tried to storm a synagogue in Halle on the Jewish holiday of Yom Kippur. When he failed to enter the synagogue, he murdered two passersby.
In an attack in 2021, a knife-wielding attacker killed one tourist and seriously injured another in the city of Dresden.
In January, a knife-wielding man described as a “stateless Palestinian” fatally stabbed two people and injured seven others on a train traveling from Kiel to Hamburg before he was arrested.