Austrian police raided 18 properties and arrested 14 people in a massive manhunt on Tuesday for possible accomplices of a convicted jihadist who shot dead four people and injured 22 others in a late-night rampage in the centre of Vienna.
The gunman, who was killed by police minutes after opening fire on crowded bars on Monday, had been released from jail less than a year ago. He was identified as Kujtim Fejzulai, a 20-year-old Austrian who also held North Macedonian nationality.
It was the first such militant attack in Vienna in a generation, and the government pledged robust action.
"We will defend our fundamental values, our way of life and our democracy with all our strength," Chancellor Sebastian Kurz said in a national address about what he branded an Islamist terror attack.
"We will find and hunt down the perpetrators, those behind this and their associates and mete out a just sentence. And we will pursue all those who have anything to do with this outrage with all available means."
Swiss police also arrested two men on Tuesday near Zurich in an investigation of possible links to the gunman.
Speaking later to broadcaster ORF, Kurz urged European nations to take more decisive action against terrorism.
"We must give everyone who wants to integrate the chance to integrate, but we must at the same time make clear that our basic values are not negotiable," he said.
The attack followed recent deadly assaults by lone Islamist attackers in Nice and Paris. Many Muslims have been angered by the publication in strictly secular France of satirical caricatures of the Prophet Mohammad.
"We Will Remain United"
In Paris, French President Emmanuel Macron visited the Austrian Embassy to write a message of condolence in German that read: "In joy and in sorrow, we will remain united."
Both he and German Chancellor Angela Merkel spoke to Kurz to offer their support as expressions of solidarity poured in from around the world.
Islamic State claimed responsibility on Tuesday for the attack without providing evidence, the group's Amaq News Agency said in a statement on Telegram.
An elderly man and woman, a young passer-by and a waitress were among those killed in the attack, Austrian Interior Minister Karl Nehammer said. A German woman was also killed, Germany's Foreign Minister Heiko Maas said.
Vienna's mayor said three people were still in critical condition.
The normally bustling centre of Vienna was largely empty on Tuesday as the public heeded government calls to stay inside and a manhunt for a possible second gunman was underway.
The gunman, armed with an assault rifle, a handgun and a machete, had opened fire at six places including a bar near Vienna's main synagogue on Monday as people enjoyed a last night out before a COVID-19 curfew took effect.
Interior Minister Nehammer said Fejzulai had recently served about eight months of a 22-month sentence for seeking to travel to Syria to join Islamic State.
"He was released early exactly because he gave the impression that he had engaged with deradicalisation programmes and was prepared to integrate himself into society," Nehammer told a news conference.
Fejzulai had posted a photo on a social media account before the attack, showing himself with weapons, Nehammer said.
Whether anyone else was involved in carrying out or preparing the attack remained unclear.
After saying overnight that another attacker was on the loose, Nehammer said there was no indication of another assailant in large volumes of mobile phone footage of the attacks sent in by the public, but it could not be ruled out.
North Macedonia's Interior Ministry said it believed three people - all born in Austria and holding dual Austrian and North Macedonian citizenship - had been involved in the attack. It identified them only by initials and gave no further information.
A man identified as Fejzulai's grandfather told a local television channel in North Macedonia that his grandson would visit his ancestral home, the tiny mountain village of Cellopek, every year.
The Band Played On
Chancellor Kurz, a conservative who takes a hard line on immigration, said: "This is not a conflict between Christians and Muslims or between Austrians and migrants... No, this is a fight between... civilisation and barbarism."
The government announced three days of national mourning.
A police spokesman said at least 1,000 officers had been involved in the search for accomplices. The army was guarding sensitive sites in Vienna to free up police for the operation.
A witness to the attack, Vienna rabbi Schlomo Hofmeister, said he had seen one shooter but could not be certain there were no others.
Videos posted on social media showed a gunman running down a cobbled street shooting and yelling. One showed a man gunning down a person outside a bar on the street where the synagogue is located, then returning to shoot the same person again.
The shooting took place as the Vienna State Opera was holding its final concert before a month-long coronavirus lockdown. Musicians played on, despite news of the violence outside: "If people weren't allowed to leave anyway, why should we stop early?" a spokeswoman said.
After the concert, with the doors still locked, four members of the orchestra came back into the pit to play a Haydn string quartet for those who were still in their seats.
US President Donald Trump tweeted: "These evil attacks against innocent people must stop. The US stands with Austria, France, and all of Europe in the fight against terrorists, including radical Islamic terrorists."
Democratic presidential candidate Joe Biden condemned what he called a "horrific terrorist attack", adding: "We must all stand united against hate and violence."
Saudi minister of state for foreign affairs Adel Al-Jubeir said on Twitter late on Tuesday that the Vienna attack was a "heinous crime... contrary to all religions and human values".