Austrian authorities said that at least 4 people were killed with 17 more injured after a few gunmen open fired at six different locations in the Austrian capital in Vienna on Monday evening.
The shootings took place at about 8 p.m. on Monday near the Seitenstettengasse synagogue at a city centre area, which was busy at the time with people in bars and restaurants, the BBC reported.
The victims comprised one woman, two men and an attacker.
Addressing a press briefing early Tuesday morning, Interior Minister Karl Nehammer described the heavily armed attacker, who was shot dead by the police, as an Islamic State (IS) sympathiser.
He added that the attackers' home had been searched and video material seized.
Nehammer urged people to stay away from the centre, as police cordoned off some streets and brought in reinforcements.
It was not immediately who was the target of the shootings, that came just hours ahead before a national lockdown was to come into effect to stem the spread of the Covid-19 pandemic.
Earlier, Nehammer had said at least one "heavily armed and dangerous" attacker was believed to be still at large, but local media reports quoted officials as saying there could have been as many as four attackers, the BBC reported.
As a mark of respect, the Austrian government has declared three days of mourning from Tuesday, with flags to fly at half-mast and a minute's silence at midday.
Austrian Chancellor Sebastian Kurz condemned the shootings, saying the incident was a "repulsive terror attack", adding "we are experiencing difficult hours in our republic".
"Our police will act decisively against the perpetrators of this hideous terrorist attack. We will never allow ourselves to be intimidated by terrorism," he said.
Kurz will address the public after a cabinet video conference on Tuesday morning.
The incident has been strongly condemned by European leaders, including French President Emmanuel Macron, who said that Europe must not "give up" in the face of attacks.
While UK Prime Minister Boris Johnson said he was "deeply shocked by the terrible attack", European Council President Charles Michel called the incident a cowardly act that violated life and human values.
US President Donald Trump described it as "yet another vile act of terrorism in Europe", and his Democratic challenger Joe Biden added: "We must all stand united against hate and violence."
The Vienna incident comes days after a string of recent terror attacks in France.
On October 16, middle-school teacher, Samuel Paty was beheaded by an 18-year-old Muslim immigrant, Abdullakh Anzorov inside a school near Paris.
Then on October 29, Brahim Aouissaoui, a 21-year-old Tunisian man, stabbed three people to death inside the Notre-Dame Basilica in the city of Nice.
