A huge manhunt was under way Tuesday (November 3rd) after gunmen opened fire at multiple locations across central Vienna, killing at least four people in what Austrian Chancellor Sebastian Kurz described as a "repulsive terror attack".

One of the gunmen had North Macedonian-Austrian nationality and a conviction for trying to travel to Syria, Austrian Interior Minister Karl Nehammer said.

Twenty-year-old Kujtim Fejzulai, who was shot dead by police, was carrying an automatic weapon, a handgun and a machete and was wearing a fake explosive belt, he told the APA news agency.

Fejzulai was a supporter of the "Islamic State of Iraq and Syria" (ISIS) and had been convicted of a terrorist offence in April last year, Nehammer said.

He was sentenced to 22 months in prison but was released on parole in December.

Nehammer said he had been on a de-radicalisation programme and had managed to secure an early release.

"The perpetrator managed to fool the de-radicalisation programme of the justice system, to fool the people in it, and to get an early release through this," the minister said.

'No evidence of other shooters'

Officers have carried out 18 raids and detained 14 people in connection with the killings, Nehammer said.

Police said they were searching for at least one more assailant still at large. But Nehammer said later Tuesday there is no evidence so far that the deadly attack was carried out by more than one shooter.

The video material evaluated by the police "does not at this time show any evidence of a second attacker", he told a press conference.

The Monday evening shooting rampage was carried out in six locations including near a synagogue and the world famous opera house in the heart of Vienna.

Helicopters were flying overhead as police sealed off the city in the hunt for other attackers, while neighbouring countries stepped up border checks.

The attack follows a spate of extremist attacks in France and triggered an outpouring of solidarity from world leaders.

Two men and two women were killed in the attack, an interior ministry spokesman said, while about 15 more have been injured, seven seriously. Police also said an officer had been hurt.

The first shots were heard at around 8 p.m. in the city centre.

"It sounded like firecrackers, then we realised it was shots," said one witness quoted by public broadcaster ORF.

A gunman "shot wildly with an automatic weapon" before police arrived and opened fire, the witness added.

Another spoke of at least 50 shots being fired.

"All the signs make it clear it is a radicalised person and a person who feels closely connected to ISIS," Nehammer said of the slain attacker.

Police had used explosives to blast their way into the apartment of the dead man who had been "heavily armed", he told a press conference.

Speaking to ORF, Kurz said the attackers "were very well equipped with automatic weapons" and had "prepared professionally".

Kurz said that while police were concentrating on the anti-terror operation, the army would take over the security of major buildings in Vienna.

Support for Austria

Germany stepped up checks at the Austrian border as Chancellor Angela Merkel said: "The fight against these assassins and those who instigate them is our common struggle."

"We French share the shock and sorrow of the Austrian people," French President Emmanuel Macron said in a social media post.

On Thursday, three people were killed at a church in the French city of Nice, and a schoolteacher was beheaded by an extremist with a connection to Syria outside Paris on October 16th.

EU Council chief Charles Michel said the bloc "strongly condemns this cowardly act".

Leaders of other nations also voiced support for Austria, among them the US, Canada, Australia, Britain, Israel, Russia, Pakistan, India, Iran and Turkey.