Gunmen opened fire at multiple locations across central Vienna on Monday, killing at least two people and wounding several more in what Austrian Chancellor Sebastian Kurz described as a "repulsive terror attack", with a huge manhunt under way for the assailants.
One of the gunmen was shot dead by police who said they were hunting for at least one more attacker still at large.
The attacks, in six locations including near a synagogue in the centre of town, were carried out by "several suspects armed with rifles", police said.
Police said one person had died, with public broadcaster ORF stating the individual was a passer-by.
Vienna mayor Michael Ludwig told ORF that a second person had died of her injuries and that 15 people had been taken to hospital, seven of them seriously wounded.
Police stated earlier that an officer had also been hurt during the assaults.
The shooting began just hours before Austria was to re-impose a coronavirus lockdown, with people out in bars and restaurants enjoying a final night of relative freedom.
The attacks started at around 8 pm (1900 GMT) when the first gunshots were heard in the city's centrally located first district.
In a press conference early Tuesday, Interior Minister Karl Nehammer said: "According to what we currently know, there is at least one attacker who is still on the run."
Speaking to ORF, Austrian leader Kurz had said that the attackers were "were very well equipped with automatic weapons" and had "prepared professionally".
Earlier, he tweeted: "Our police will act decisively against the perpetrators of this repulsive terror attack," adding that "we will never be intimidated by terrorism and we will fight this attack with all means".
Kurz said that while police were concentrating on the anti-terror operation, the army would take over the security of major buildings in Vienna.
Nehammer urged Vienna residents to remain in their homes and keep away from all public places or public transport. He said that children would not be expected at school on Tuesday in Vienna.
Sirens and helicopters could be heard in the city centre as emergency services responded to the attack.
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 initial shooting was 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 temple 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.
- 'Cowardly act' -
"It sounded like firecrackers, then we realised it was shots," said one eyewitness quoted by public broadcaster ORF.
A shooter had "shot wildly with an automatic weapon" before police arrived and opened fire, the witness added.
Austria had until now been spared the sort of major attacks that have hit other European countries.
President Emmanuel Macron of France, which has experienced two serious attacks in recent weeks, tweeted that "we French share the shock and sorrow of the Austrian people".
"After France, it's a friendly nation that has been attacked," he added, referring to the killing on Thursday of three people by an attacker in the southern city of Nice and the beheading of a schoolteacher by a suspected Islamist outside Paris several days before.
EU Council chief Charles Michel tweeted that the bloc "strongly condemns this cowardly act".
And Germany's foreign ministry tweeted that the reports from Austria were "horrifying and disturbing".
"We can't give in to hatred that is aimed at dividing our societies," the ministry added.
Czech police said they were conducting checks on the border with Austria.
"Police are carrying out random checks of vehicles and passengers on border crossings with Austria as a preventive measure in relation to the terror attack in Vienna," Czech police tweeted.
Italian Prime Minister Giuseppe Conte also "strongly condemned" the shootings.
"There is no room for hatred and violence in our common European home," he said on Twitter in Italian and German.