At least two people have been killed in a nightclub shooting in the town of Constance, Germany.

A man opened fire at a club called Grey around 4.30 am local time on Sunday (30 June), killing one person. The suspect also died following an exchange of fire with the police.

At least three people are believe to have been seriously injured in the accident. One of them was a doorman, thought to have been shot as he tried to hinder the attacker.

One policeman was also injured. His injuries are not thought to be life-threatening.

"Guests were able to save themselves by fleeing outside or hiding," the police said in a statement, according to Deutsche Welle.

The police added special units and a helicopter had been deployed to the scene.

The motive behind the attack is not known yet. However, police ruled out terrorism, according to Reuters.

"We are still investigating but the circumstances surrounding the events at the disco in the evening before the shooting are a bit clearer and this led us to rule out a terrorism background," a police spokesperson said.

Authorities said the shooter was an Iraqi citizen living in Germany. He was not an asylum seeker.

The shooting occurred just days after one person was killed in a knife attack at a supermarket in the city of Hamburg.

The 26-year-old suspect stabbed one person to death and wounded another six. It is believed he was known to authorities as a suspected Islamic radical, but he also was psychologically unstable, German officials said.