Six people were killed and another two wounded in a shooting in the town of Rot am See in Germany's south-west, police say.

The suspect's parents were among the dead and the other victims also were believed to be relatives.

A man called police shortly after 12.45pm (local time) on Friday and told them he had killed several people, regional police chief Reiner Moeller said at a news conference.

Police kept the man on the line and, when they arrived at the scene several minutes later, arrested a 26-year-old German national as the suspect in the slayings, Mr Moeller said.

Officers found the bodies of six people — three women and three men, ages 36 to 69 — in and behind a building where a bar is located.

Another two people were hurt, and one of them has life-threatening injuries, Mr Moeller said. The suspect also threatened two children, ages 12 and 14.

The suspect had a licence to own firearms as a shooting club member, Mr Moeller said. Authorities believe he used a semi-automatic pistol.

Forensic experts enter the building where the shooting took place. ( Reuters: Ralph Orlowski )

"We can't say anything so far about the motive," he said.

"Because of the victims and the wounded, we believe it was a family drama, since according to what we know at present all were related to each other."

The suspect's mother and father were among the dead and there was no indication that there were additional perpetrators, police said.

Rot am See, a town of several thousand, is located some 135 kilometres south-east of Frankfurt.

Gun control laws in Germany are among the most stringent in Europe.

In 2002, a massacre of 16 people by a 19-year-old shooter at a high school in the city of Erfurt saw the country increase restrictions on gun ownership.

A 17-year-old killed 15 people at a high school in the southwestern town of Winnenden in 2009, seeing a further tightening of gun laws.

ABC/wires