At least three people were killed and 15 seriously injured in a serious terrorist attack in Vienna on Monday evening.
Police said Tuesday morning they believe the attack was motivated by Islamist extremism.
So far, authorities have indicated that at least one person carried out the attack with an assault rifle and multiple handguns. He was shot by the police and his home was searched during the night.
Police are still working to determine if anyone else was involved in orchestrating and conducting the attack.
Video footage sent by eyewitnesses to the Financial Times recorded dozens of footage and heavily armed police response teams in Vienna's old town shortly before 8 p.m. on Monday evening near the city's main synagogue.
Chancellor Sebastian Kurz ordered the army to be deployed to protect sensitive areas across the country after the attack.
“We are experiencing difficult times in our republic. . . Our police will take decisive action against those responsible for this disgusting terrorist attack, ”tweeted Mr Kurz.
Authorities stopped all public transport in the city center and asked all residents to stay inside. The schools should close on Tuesday until further notice.
Austrian police officers guard the Vienna State Opera © CHRISTIAN BRUNA / EPA-EFE / Shutterstock
Oskar Deutsch, a Jewish community leader, said it was unclear whether the synagogue had been targeted. He said the city temple and its adjoining office were closed at the time of the incident.
Karl Nehammer, Austria's interior minister, told the ORF television broadcaster that the city was suffering "an obvious terrorist attack" and warned that the "situation was still developing". "We assume there were several armed men," he said. "Unfortunately, several people are injured and some people were likely killed."
"Vienna is in a state of emergency," said Andreas Peter, a local official from the city's rescue service.
The Viennese police patrol a street in the Austrian capital
The video material broadcast by the broadcaster Oe24 showed a masked shooter firing in the middle of a Viennese street and a pool of blood in front of a restaurant.
French President Emmanuel Macron tweeted that France shared "the shock and pain of the Austrian people who were struck tonight by an attack in the heart of their capital Vienna".
"After France, it is a friendly country that is under attack," he said. “This is our Europe. Our enemies need to know who they are dealing with. We won't give them anything. "
He spoke just days after a man armed with a knife killed three people in a church in the southern French city of Nice in an apparent Islamist terrorist attack.
Last month a Chechen refugee killed a French teacher, Samuel Paty, on the street outside his school and said he was taking revenge on Paty, who was showing two cartoons to students in a lesson on free speech.