Two persons have been killed and several people, including a police officer, sustained injuries in multiple shootings that took place in six different locations in Austrian capital Vienna on Monday evening.

Police said several shots were fired shortly after 8 pm on a lively street in the city centre and that there were six shooting locations. Austria's top security official said that authorities believe there were several gunmen involved and that a police operation was still going on hours later.

The shootings appeared to be a terrorist attack with multiple perpetrators, according to Austrian Interior Minister Karl Nehammer, Xinhua news agency reported.

“I am glad that our police were able to neutralise one of the attackers," Austrian Chancellor Sebastian Kurz said. "We will never allow ourselves to be intimidated by terrorism and will fight these attacks with all means," he added.

There were several people injured, the Vienna police said on Twitter. According to a ministry spokeswoman, a police officer was shot and seriously injured in the exchange of fire near Schwedenplatz. "We are with all possible forces in action," wrote the police on Twitter, calling on people to avoid all public places in the city.

Videos broadcast by private broadcaster "Oe24" showed a masked shooter who fired at least two shots in the street. Another video showed a large pool of blood outside a restaurant. 

Oskar Deutsch, president of the Jewish Community of Vienna, said that it is not clear whether the city temple was one of the targets. "What is certain, however, is that both the synagogue in Seitenstettengasse and the office building at the same address were no longer in operation and closed at the time of the first shots," he wrote on Twitter.