At least seven people have been killed and several others wounded after a mass shooting at a Jehovah’s Witness church in the German city of Hamburg.

Seven people were reportedly seriously wounded while 17 more had minor injuries.

The gunman is believed to be among several dead found in the building, according to local police.

“We have no indications of a perpetrator on the run,” a police spokesman said, adding that investigators instead have “indications that a perpetrator may have been in the building and may be even among the dead.”

Two witnesses interviewed on n-tv television, whose names weren’t given, said they heard 12 shots.

Police said on Twitter that a large operation was under way in the city’s Alsterdorf district.

The scene of the shooting was the Jehovah’s Witnesses’ Kingdom Hall, a modern and boxy three-storey building next door to an auto repair shop.

Police spokesman Holger Vehren said police were alerted to the shooting about 9:15 p.m. and were on the scene quickly.

He said that after officers arrived and found people with apparent gunshot wounds on the ground floor, they heard a shot from an upper floor and found a fatally wounded person upstairs who may have been a shooter.

He said police did not have to use their firearms.

Vehren said there was no indication that a shooter was on the run and that it appeared likely that the perpetrator was either in the building or among the dead.

Armed police officers near the scene of a shooting in Hamburg, Germany. Photo / AP

Police had no information on the event that was under way in the building when the shooting took place. They also had no immediate information on a possible motive.

Hamburg police said: “According to initial findings, a shot was fired in a church on Deelböge St in the GroßBorstel district.

“Several people were seriously injured, some fatally. We are on site with a large contingent of forces.

“So far, there is no reliable information on the motive for the crime.”

It is understood the church was hosting an event that had started at 7pm local time, two hours before the shooting broke out.

Hamburg Mayor Peter Tschentscher said the early reports from the scene were “shocking”.

“My deepest condolences to the families of the victims.

“The emergency services are working flat out to track down the perpetrators and clarify the background.”

An emergency alert sent to people in the area said the shootings took place at a church at about 9.15pm local time.

“One or more unknown perpetrators shot(s) at people in a church,” it said.

Locals were asked to avoid the area.

The area is a few kilometres north of the downtown area of Hamburg, which is Germany’s second-biggest city.