Police said there was “one deceased person” and several injured, including one police officer.
Meanwhile, one suspect was “shot and killed by police officers,” Vienna police said on their Twitter account.
The attack had been carried out by “several suspects armed with rifles”, and police added that there had been “six different shooting locations”.
Gunshots were fired at around 8:00 pm local time (1900 GMT), beginning at the Seitenstettengasse in the city´s centrally-located first district.
The shooting began just hours before Austria was to re-impose a coronavirus lockdown to try to slow the spread of Covid-19, and bars and restaurants were packed as people enjoyed a final night of relative freedom.
Austrian Interior Minister Karl Nehammer told public broadcaster ORF that the incident “appeared to be a terrorist attack” and urged Viennese to remain in their homes.
Nehammer repeated police appeals to residents to keep away from all public places or public transport, and frequent sirens and helicopters could be heard in the city centre as emergency services responded to the incident.
An AFP photographer said that large numbers of police were guarding an area near the city´s world-famous opera house.
The location of the incident is close to a major synagogue.
The president of Vienna´s Jewish community Oskar Deutsch said that shots had been fired “in the immediate vicinity” of the Stadttempel synagogue, but added that it was currently unknown whether the synagogue itself had been the target of an attack.
He said that the synagogue and office buildings at the same address had been closed at the time of the attack.