More than a million migrants have entered Germany over the past year, many fleeing war in Afghanistan, Syria and Iraq
A 27-year-old Syrian man denied asylum in Germany a year ago died on Sunday when he set off a bomb outside a crowded music festival in Bavaria, an official said, in the fourth violent attack in the country in less than a week.
Police said a dozen people were wounded, including three seriously, in the attack in Ansbach, a town of 40,000 people southwest of Nuremberg that is also home to a U.S. Army base.
The incident will fuel growing public unease about Chancellor Angela Merkel's open-door refugee policy, under which more than a million migrants have entered Germany over the past year, many fleeing war in Afghanistan, Syria and Iraq.
The dead man had been in treatment after twice before trying to kill himself, though Sunday's explosion was more than just "a pure suicide attempt", Bavarian Interior Minister Joachim Herrmann told Reuters.
An Islamist link could not be ruled out, he earlier told reporters.
"It's terrible ... that someone who came into our country to seek shelter has now committed such a heinous act and injured a large number of people who are at home here, some seriously," Herrmann told a hastily convened news conference early on Monday.
"It's a further, horrific attack that will increase the already growing security concerns of our citizens. We must do everything possible to prevent the spread of such violence in our country by people who came here to ask for asylum."
He told Reuters the recent attacks raised serious questions about Germany's asylum law and security across the country and said he planned to introduce measures at a Bavarian government meeting on Tuesday to strengthen the police forces and ensure they have adequate equipment.
Herrmann said the man arrived in Germany two years ago and had been in trouble with local police repeatedly for drug-taking and other offences.
He said investigators had yet to determine the motive of the attacks. "Because the rucksack and this bomb were packed with so many metal parts that could have killed and injured many more people, it cannot simply be considered a pure suicide attempt."
It was the second violent incident in Germany on Sunday and the fourth in the last week, including the killing of nine people by a deranged 18-year-old Iranian-German gunman in Munich on Friday.
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Herrmann said the man, whose identity has not yet been released, had been living in Ansbach for a year. Although his application for asylum had been denied, he was not in danger of being deported immediately given the civil war in Syria.
One U.S. intelligence official, speaking on condition of anonymity, said investigators would focus on what the bomber was doing before he left Syria and why he was denied asylum.
U.S. sources said the bombing did not appear to be a well-planned operation and could well turn out to be the act of another deranged individual.
Herrmann said the man had been denied entry to the Ansbach Open music festival shortly before detonating the bomb outside a restaurant called Eugens Weinstube.
More than 2,000 people were evacuated from the festival after the explosion, police said. A large area around the blast site remained blocked off hours later.
Ansbach resident Thomas Debinski said people panicked when they heard the explosion, especially after the events of the past week.
"Suddenly you heard a loud, a really loud bang, it was like an exploding sound, definitely an explosion," he said. "(People were) definitely panicking."
Debinski said it soon became clear that someone had set off a bomb in a rucksack.
Earlier on Sunday, a 21-year-old Syrian refugee was arrested after killing a pregnant woman and wounding two people with a machete in the southwestern city of Reutlingen, near Stuttgart.
"After what just happened in Munich, and today in Reutlingen, what you hear about, it is very disturbing, when you know that such a thing can happen so close to you, in such a small town as Ansbach," Debinski said.
A week ago a 17-year-old who had sought asylum in Germany was shot dead by police after wounding five people with an axe near Wuerzburg, also in Bavaria. He was initially thought to be Afghan but federal Interior Minister Thomas de Maiziere has since said he may have been from Pakistan.
Police said neither Sunday's machete attack nor Friday's shooting in Munich bore any sign of connections with Islamic State or other militant groups.
Islamic State claimed responsibility for the Wuerzburg attack as well as the July 14 rampage in the French Riviera city of Nice, in which a Tunisian man drove a truck into Bastille Day crowds, killing 84 people.