Two people have been killed, including one suspect, and multiple injured following an "apparent" terror attack near a synagogue in central Vienna.
Vienna police said there had been "several" exchanges of fire in the city's central Innere Stadt, an area with numerous bars and restaurants.
One attacker was "dead" and another "on the run", while one police officer had been seriously injured, Austria's interior ministry said according to news agency APA.
Viennese police on Twitter warned locals to stay away from public places and public transport.
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Speaking to Austrian media, Nehammer said there were "probably also fatalities" as well as several people injured. "We are on site with all available forces".
Police added that the exact circumstances of the incident were still being determined. The police operation is taking place in the centre of Vienna, close to the Danube river.
Austrian public broadcaster ORF cited witnesses saying several shots were fired shortly after 7pm. Police said trams and buses weren't stopping and urged social media users not to post videos of the ongoing police operation, so as not to endanger officers.
The attackers targeted the area around the Stadttempel, Vienna's Jewish synagogue dating back to the 1820s, on Monday evening. Some reports said one perpetrator detonated an explosive belt, but the reports were not confirmed and few others said they heard any large explosions.
This is a developing story.