Herrmann told a press conference in Nuremburg that the 27-year-old Syrian, who arrived in Germany in July 2014, had in the video declared his allegiance to Abu Bakr al-Baghdadi, Islamic State's (IS) top leader.

The detonation outside an Ansbach cafe and close to an outdoor concert on Sunday evening wounded 15 people, many seriously, and killed the suspected bomber, who was carrying a rucksack.

Herrmann says Syrian left video statement on cell phone

The Ansbach bombing was the fourth violent attack to rock Germany over

the past week. Three of them were perpetrated by recent immigrants.

"A video made by the assailant was found on his mobile phone in which he threatened an attack," Herrmann said, referring to the Ansbach bombing.

Shortly after Herrmann's announcement, Islamic State's mouthpiece, the agency Aamaq, claimed that the Ansbach perpetrator had been one of IS' "soldiers."

German authorities have not yet identified the 27-year-old.

"After that he announced in the name of Allah that he pledged allegiance to (IS chief) Abu Bakr al-Baghdadi, the well-known Islamist leader, and he announced an act of revenge against Germans because they were standing in the way of Islam." Herrmann said.

Watch video 01:23 Herrmann: Suspect left IS-linked video

Herrmann said two weeks ago the federal BAMF agency for migration and refugees had ordered the Syrian to leave Germany and return to Bulgaria, where he had first applied for asylum.

Police had earlier said the man intended to target the open-air festival but was turned away as he did not have a ticket. More than 2,500 people had gathered for the concert.

De Maiziere: Existing laws sufficient

Simultaneously, at a Berlin press conference on Monday, Federal Interior Minister Thomas de Maiziere said police investigators were working quickly and thoroughly to establish whether there might be terrorist links to organizations such as IS in the Ansbach bombing.

He said the rejected Syrian asylum-seeker had twice attempted to take his life and had been in psychiatric treatment.

De Maiziere says police will strengthen patrols at airports.

"It could be a combination of both," de Maiziere said.

Germany's existing laws were sufficient for authorities to respond to a series of attacks across Germany over the past week, including Wurzburg, Munich, Reutlingen and Ansbach, de Maiziere said.

He was responding to a question on whether Germany's Bundeswehr armed forces should also be used within Germany.

This was permitted on the basis of rulings by Germany's constitutional court but only in extremely difficult situations, he added.

The presence of federal police (Bundespolizei) would be intensified at airports and railway stations, he said.

Europe will defend itself, says EU

The EU reacted to the attacks, saying that compassion for refugees would not come at the expense of security in the bloc.

"Europe's doors are open to those who flee war and persecution and who seek asylum, but we will defend ourselves against attacks on our way of life," European Commission spokesman Margaritis Schinas told journalists in Brussels.

"Our sense of compassion does not and must not come at the expense of

our security," he said.

ipj/kms (AFP, AP, dpa, Reuters)