The Austrian government on Friday ordered the closure of two mosques, frequented by an Islamist militant who killed four people in Vienna.
Two mosques are located on the outskirts of Vienna - one called Melit Ibrahim in the Otakring district and the other Tawhid in the Majdling area.
The Austrian Integration Minister Susanne Raab said that the local intelligence agency BVT had assessed that "visits to these mosques have accelerated the attacker's radicalization".
The attacker, identified by Austrian authorities as Kujtim Fejzullai, originally an Albanian from North Macedonia, carried out the attack on Monday, opening fire at six locations in central Vienna.
Two women and two men were killed and 23 people were wounded.
Police killed the attacker and discovered that he had both Austrian and Macedonian citizenship.
The attacker traveled to Turkey in 2018, in an attempt to join Islamic State militants in Syria, but was captured and sent back to Austria.
The Islamic State militant group has said it is behind the attack in Vienna.
On Friday, police in Germany also said they had raided the homes of four people over alleged links to the Vienna attacker.
Police said they are not considered suspects but have had contact with the attacker and two of them have met him in person.
The raids took place in Kassel, Osnabrück, and Pineberg, near Hamburg.