The Syrian man who blew himself up in Ansbach, Germany, on Sunday made a video pledging allegiance to the leader of so-called Islamic State, Bavaria's interior minister says, BBC reported.
Joachim Hermann said two phones, multiple SIM cards and a laptop were found with the body of the 27-year-old asylum seeker or at his accommodation.
The man threatened a "revenge attack" on Germans in the video, he said.
IS has claimed it was behind the attack and the Syrian was an IS "soldier".
Fifteen people were injured, four of them seriously, when the man's explosive device went off close to a music festival in the small town, which is near Nuremberg.
The attacker announced in the video "in the name of Allah that he pledged allegiance to [IS chief] Abu Bakr al-Baghdadi... and announced an act of revenge against Germans because they were standing in the way of Islam," Mr Hermann said.
Germany was already reeling after five people were wounded on a train in another part of Bavaria a week ago by an axe-wielding teenager from Afghanistan who had pledged allegiance to IS.
On Friday nine people were killed by a teenage gunman in the state capital, Munich, who then shot himself dead. That incident was not believed to be jihadist-inspired.