A lone gunman opened fire during a lecture at Heidelberg University in south-western Germany and wounded four people, some of them seriously, police have said.

Police said the perpetrator was dead but did not give details of how that happened.

They had earlier asked people on Twitter to avoid the Neuenheimer Feld area, home to a large university campus.

Authorities would not confirm a report by German news agency dpa that one victim died of her injuries a few hours after being shot in the head, citing unidentified security sources.

The man opened fire with a long-barrelled firearm in a lecture hall and then fled outside, police said.

They stressed that they believe he was acting alone and there was no longer any danger.

There was no immediate word on a possible motive.

The dpa agency cited unidentified security sources as saying that the gunman killed himself.

It also reported, without citing sources, that the gunman is believed to have been a student himself and that security officials say initial indications are that he did not have any political or religious motive.

Heidelberg is located south of Frankfurt and has about 160,000 inhabitants.

Its university is one of Germany’s best-known.