Key Points
- Several people have been shot and killed at a church in Hamburg in northern Germany.
- Authorities say a perpetrator is among the dead.
- The incident occurred at around 9pm local time.
Hamburg mayor Peter Tschentscher says the attack on a Jehovah's Witness church is "shocking".
"My deepest sympathy goes to the relatives of the victims," he wrote in a message on Twitter.
A police operation involving special forces officers is underway.
What do we know so far?
Several people have been killed in a shooting in a church in the Gross Borstel district of Hamburg, German police said.
Police did not give an exact figure but German media report at least seven people have been killed and many more injured.
"According to first indications, shots were fired in a church in Deelboege street in the Grossborstel district. Several people were seriously injured, some even fatally," police said on Twitter.
The shooting took place at around 9pm local time, they added.

Police were alerted about the attack 15 minutes after it happened. Source: AAP / Jonas Walzberg
Residents must stay indoors and avoid the area, police said, adding that streets surrounding the church have been cordoned off.
Are there any casualties?
Police did not give an exact toll, but German media outlets said six people were killed.
The gunman is believed to be among several dead found in the building, police said Thursday.
"We have no indications of a perpetrator on the run," a police spokesman at the scene said, adding that investigators instead have "indications that a perpetrator may have been in the building and may be even among the dead."
Who are the perpetrators?
It is so far unclear how many perpetrators were involved or who they are. Police said more information will follow.
"At the moment there is no reliable information on the motive of the crime," they added.
Police have urged people not to speculate on why the attack was carried out.

Witnesses reported hearing as many as 12 shots from the building. Source: AAP / Daniel Bockwoldt
Who are the Jehovah's Witnesses?
Jehovah's Witnesses is a US Christian movement set up in the late 19th century that preaches non-violence and is known for door-to-door evangelism.
The denomination has 175,000 members in Germany, including 3,800 in Hamburg.
Has there been comparable violence in Germany?
Germany has been rocked by several attacks in recent years, which authorities said involved terrorism.
Among the deadliest was a truck rampage at a Berlin Christmas market in .
In February 2020, dead 10 people and wounded five others in the city of Hanau.
And in 2019, two people were killed after a neo-Nazi tried to storm a synagogue in .