HAMBURG, March 9 (Reuters) - Several people were killed in a shooting at a Jehovah's Witness church in the northern German city of Hamburg on Thursday, with the motive for the attack unclear, police said.

A perpetrator may be among the dead, police said. Several people were seriously injured, police said, declining to say how many died.

The Bild newspaper reported that seven people were dead and eight others injured in the shooting at the Kingdom Hall of Jehovah's Witness in a northern district of Hamburg.

Police received a call soon after 9 p.m. (2000 GMT), a spokesperson said. Officers quickly arrived at the scene to find several people seriously injured and some dead.

"Then they heard a shot from above, they went upstairs and found one further person," said the police spokesperson.

Hamburg police tweeted that they believed a dead person they had found could be a perpetrator. "In order to rule out the involvement of further perpetrators, we are conducting comprehensive checks and searches," they said.

Germany's DPA news agency, citing a reporter on the scene, said that local residents in the northern Alsterdorf district of Hamburg had received warnings on their mobile phones of a "life threatening situation" and that streets had been sealed off.

Television footage showed dozens of police cars as well as fire engines blocking off streets and some people, wrapped in blankets, being led by emergency service workers into a bus.

"We heard shots," one unnamed witness told reporters. "There were 12 continuous shots," he said. "Then we saw how people were taken away in black bags."

Germany has been shaken by a number of shootings in the last few years. In February 2020, a gunman with suspected far-right links shot dead nine people, including migrants from Turkey, in the western town of Hanau before killing himself and his mother.

In October 2019, a gunman killed two people after opening fire outside a German synagogue in the eastern city of Halle on the Jewish holy day of Yom Kippur.

The mayor of Hamburg, home to Germany's biggest port, expressed shock.

"I extend my deepest sympathy to the families of the victims. The forces are working at full speed to pursue the perpetrators and clarify the background," tweeted Peter Tschentscher.