Austrian authorities say they have detained 14 people in connection with what Chancellor Sebastian Kurz described as a "repulsive terror attack" in Vienna that killed four people.
Police urged people to stay indoors as they hunt for suspects after gunmen opened fire at six locations in the city center on the evening of November 2.
Two men and two women died of their wounds and 22 other people were wounded.
Police shot dead a suspect identified as a 20-year-old dual national of Austria and North Macedonia who had a previous terror conviction. Two other suspects were also said to have Macedonian roots.
The extremist Islamic State (IS) group claimed responsibility for the attack via its Amaq news agency, without providing evidence.
Police conducted a series of raids in Vienna and Lower Austria, Interior Minister Karl Nehammer said on November 3, adding that they have found no evidence that a second shooter was involved.
The attacker was named as Kujtim Fejzulai, a man born in Austria with roots in North Macedonia who was sentenced to 22 months in prison in April last year because he had tried to travel to Syria to join the Islamic State extremist group. He was granted early release in December.
He "managed to fool the deradicalization program of the justice system, to fool the people in it, and to get an early release through this," Nehammer told a press conference.
The minister earlier said the dead assailant had been convicted under a law that punishes membership in terrorist organizations.
In a statement posted on Telegram, IS claimed that one of its followers, whom it identified as Abu Dagnah Al-Albany, used a gun and a machine gun to target crowds in Vienna before being shot by police.
North Macedonia’s Interior Ministry said that, according to a list of suspects provided by Austrian police, two other dual citizens of Austria and North Macedonia are suspected of involvement in the Vienna attack.
The ministry, which vowed to cooperate fully with Austrian authorities in the the case, said the two suspects, identified as A.G. and U.A., were born in Austria.
In Switzerland, police announced the detention of two Swiss men aged 18 and 24 near Zurich, saying: "The extent to which there is a connection between the two people arrested and the alleged assassin is currently the subject of investigation."
Nehammer said that 1,000 security personnel had been deployed for the manhunt while neighboring countries had offered assistance.
A 28-year-old police officer who had been wounded during the attack was not in a life-threatening condition anymore, he said.
The Austrian news agency APA, citing a Health Association spokeswoman, reported that seven of those wounded were in a critical life-threatening condition.
The attack took place in an area busy with people in bars and restaurants, near Vienna's central synagogue, just hours before Austria was to reimpose a coronavirus lockdown.
Kurz delivered a message of national unity on November 3 as he addressed his country and declared three days of mourning.
"We will never allow this hatred to gain ground," the chancellor said in a televised speech.
"We must be aware that this is not a conflict between Christians and Muslims or between Austrians and migrants," Kurz added.
"Our enemy -- Islamist terrorism -- does not only want to cause death and pain, but it wants to split our society," he said, vowing that Austria would defend its democracy, fundamental rights and its liberal way of life.
The mourning will last until November 5, the government decided.