Police said a dozen people were wounded, including three seriously, in the attack in Ansbach, a town of 40,000 people southwest of Nuremberg.
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."
Herrmann told Reuters 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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