German police said on Friday they were conducting searches in several German towns in connection with four people believed to have ties to the suspected Vienna attacker who killed four people when he opened fire on bystanders and bars on Monday.
Vienna police shot dead the 20-year-old dual citizen of Austria and North Macedonia who had previously been jailed for trying to join Islamic State in Syria.
Germany's BKA criminal police said on Twitter that they were searching homes and businesses in the German towns of Osnabrueck, Kassel and in the district of Pinneberg near Hamburg.
"There is no initial suspicion that the four people affected by today's measures took part in the attack but there are believed to have been links with the suspected attacker," they said.
The search warrants were obtained after the Austrian judiciary transferred information to German prosecutors, the BKA said.
Switzerland has also arrested two men in connection with Monday's attack, and Austria was in close contact with another unspecified country in its investigation, Austrian Interior Minister Karl Nehammer had said on Thursday.
All 15 people arrested in Austria in connection with the deadly rampage are part of the radical Islamist scene, Austrian Interior Ministry officials have said.