A failed asylum-seeker from Syria blew himself up and wounded 15 people after being turned away from an open-air music festival in southern Germany, authorities said Monday. It was the fourth attack to shake Germany in a week — three of them carried out by recent migrants.

The 27-year-old, whom authorities have not identified, set off a backpack laden with explosives and sharp bits of metal outside a wine bar Sunday night after being refused entry to the nearby festival in the southern town of Ansbach because he didn’t have a ticket.

Roman Fertinger, the deputy police chief in nearby Nuremberg, said there likely would have been more casualties if the man had managed to enter the concert venue.

Four of the 15 victims suffered serious injuries in the blast.

“My personal view is that I unfortunately think it’s very likely this really was an Islamist suicide attack,” Bavarian interior minister Joachim Herrmann told German news agency dpa. No group immediately claimed responsibility.

Herrmann said the man’s request for asylum was rejected a year ago, and a spokesman for Germany’s interior ministry said he had received two deportation notices.

Tobias Plate said the man was most recently told on July 13 that he would be deported to Bulgaria, where he submitted his first asylum request.

Plate told reporters that the first deportation notice was issued on Dec. 22, 2014, but it wasn’t clear why he hadn’t been deported then. Asylum-seekers are routinely deported back to the first country where they registered if they don’t follow proper procedures, even if they’re considered to have a legitimate claim for asylum.

The unnamed man had repeatedly received psychiatric treatment, including twice for attempted suicide, authorities said, and had been known to police for drug possession.

Authorities on Monday morning raided the asylum shelter where he lived in the suburbs of Ansbach and searched his room.

One resident there said he had occasionally drunk coffee with the attacker and they had discussed religion. Alireza Khodadadi told The Associated Press that the man, whom he would identify only as Mohammed, had told him that the extremist Islamic State group was not representative of Islam.

“He always said that, no, I’m not with them, I don’t like them and such stuff. But I think he had some issues because, you know, he told lies so often without any reason, and I understand that he wants to be in the center of (attention), you know, he needed (attention),” Khodadadi said.

A team of 30 investigators was interviewing the man’s acquaintances and examining evidence collected from his home.

Asked whether the bomber might have links to the Islamic State group, Herrmann said that couldn’t be ruled out, though there was no concrete evidence yet.

“The obvious intention to kill more people indicates an Islamist connection,” he told dpa.

Authorities said they were alerted to the explosion in Ansbach’s city’s center shortly after 10 p.m.

Police said the Syrian blew himself up in the outside seating area of a wine bar near the open-air concert.

They said in a statement that security staff noticed the man with the backpack near the entrance of the concert site around 9:45 p.m.

Police spokeswoman Elke Schoenwald said he was refused entry to the concert because he didn’t have a ticket. He then sat down on a chair outside the nearby restaurant. According to witness accounts he briefly leaned forward at 10:10 p.m. and then triggered the explosion.

About 2,500 people were attending the three-day open-air concert was underway. It was shut down as a precaution after the explosion.

Bavarian public broadcaster Bayerische Rundfunk reported that 200 police officers and 350 rescue personnel were brought in.

The explosion came as Germany, and the southern state of Bavaria in particular, have been on edge.

Earlier Sunday, a Syrian man killed a woman with a machete and wounded two others outside a bus station in the southwestern city of Reutlingen before being arrested. Police said there were no indications pointing to terrorism and the attacker and the woman worked together in the same restaurant. Polish authorities said she was a Polish citizen.

Two days earlier, a man went on a deadly rampage at a Munich mall, killing nine people and leaving dozens wounded.

And an ax attack on a train near Wuerzburg last Monday wounded five. A 17-year-old Afghan asylum-seeker was shot and killed by police as he fled the scene. The Islamic IS group claimed responsibility for the attack.

These attacks came shortly after a Tunisian man driving a truck killed 84 people when he plowed through a festive crowd celebrating Bastille Day in Nice, along the famed French Riviera.

In Munich on Sunday evening, 1,500 people gathered at the scene of the shooting there, lighting candles and placing flowers in tribute to the victims of an 18-year-old German-Iranian. Police said that he had planned the attack for a year.

Munich authorities said Monday at a news conference that a 16-year-old Afghan friend of the Munich attacker may have known of the attack in advance.

Police said Monday the teenager was arrested late Sunday and investigators were able to retrieve a deleted chat between him and the attacker on the messaging app WhatsApp.

Police say that from the chat it appears that the 16-year-old met with the attacker immediately before the attack at the scene of the rampage — a mall in Munich — before the attack. He also knew the attacker had a pistol.

Investigators say the two teenagers met last year as in-patients at a psychiatric ward. Both were being treated for online game addiction, among other things.

(AP)