A Syrian refugee has been killed setting off a bomb at a bar in southern Germany which also wounded a dozen other people late Sunday, authorities say, the third attack to hit Bavaria in a week.

A Syrian refugee has been killed setting off a bomb at a bar in southern Germany which also wounded a dozen other people late Sunday, authorities say, the third attack to hit Bavaria in a week.

The 27-year-old man, whose asylum application was rejected a year ago, had been targeting a nearby pop music festival, regional interior minister Joachim Herrmann said, according to DPA.

Some 2,500 people have been evacuated from the concert after the explosion went off in front of a bar in the centre of Ansbach at around 10:00 pm (2000 GMT).

Police have blocked off the city centre and emergency services were at the scene. Bomb experts were also on their way to determine the cause of the blast.

"An explosion went off in the city centre and a man, who the latest enquiries show caused it, was killed in the event," police said in a statement.

A dozen people were wounded in the explosion, three of them seriously, added a spokeswoman, without giving any more details.

Michael Siefener, a spokesman for the regional interior ministry, said the explosion "was set off deliberately," adding that authorities were trying to establish the exact cause.

The blast is the third incident to hit the southern German state of Bavaria in a week, after nine were killed in a shooting rampage in Munich and several were wounded in an axe attack on a train.

Europe has been on edge for months after a string of deadly attacks claimed by the Islamic State jihadist group, including bombings in Brussels and carnage at Bastille Day celebrations in the southern French city of Nice.

Police released more details of Munich attacker David Ali Sonboly on Sunday, saying the 18-year-old was depressed and had spent two months in a psychiatric unit last year.

The Afghan teen was obsessed with mass killings and spent a year preparing for the gun attack that killed nine people, most of them foreigners.

At least 35 people were also wounded during Sonboly's shooting spree, which began at a McDonald's branch and ended with him turning his 9mm Glock pistol on himself.

Investigators have ruled out any link with the Takfiris, though he appears to have planned the assault with chilling precision.

Police have also arrested a 16-year-old friend in connection with the attack.

Hundreds of people, many of them in tears, gathered outside the Munich shopping centre where the attack took place to pay tribute to the victims on Sunday.

Already steeped in grief and shock, Germans were further rattled by news that a Syrian refugee had killed 45-year-old Polish woman with a machete in the city of Reutlingen.

Police said that incident on Sunday, in which three others were injured, did not bear the hallmarks of a "terrorist attack".

"When a man and woman have an argument, we assume that we are dealing with a crime of passion," a local police spokeswoman told German news agency DPA.

Three people were also injured in the attack, which ended when the 21-year-old assailant was hit by a BMW.

NTV showed amateur video footage of the suspect running away from the scene before cutting to him lying on the ground, his face bloodied and his hands cuffed by police.