One mosque has been ordered to close and another, which is officially considered an association, has also been decided to close.
This was announced by the country's integration minister Susanne Raab at a press conference on Friday.
The Minister of the Interior: "Unacceptable mistakes" were made
Vienna's police chief and Interior Minister Karl Nehammer also criticized the handling of the case.
Nehammer stated that "unacceptable mistakes" were made in the information transfer and assessment of the threat picture.
In particular, a tip from Slovakia regarding an Austrian citizen who tried to buy ammunition was not handled correctly.
According to police, suspects located and detained during raids in Germany have spent time with the perpetrator.
According to the police's previous information, 14 people have been arrested after the act.
Killed several
However, testimonies and videos from the incident indicate that the perpetrator, identified as 20-year-old Kujtim Fejzulai, carried out the attack himself.
Armed with automatic weapons and a fake bomb belt, he killed four people and injured 24, before he himself was shot dead.
Fejzulai was born in Austria but also had citizenship in northern Macedonia.
He is said to have previously expressed sympathy for the Islamic State and ended up on the police radar in connection with his attempt to travel to Syria to join the terrorist sect.