Organisers have cancelled three Taylor Swift concerts in Austria after authorities said they foiled a terror attack planned for the Vienna leg of her blockbuster Eras tour.

The decision - which could come at significant costs to Vienna's businesses - has devastated fans and renewed focus on the vulnerability of huge concerts as soft targets for terror networks and spree killers.

"Due to confirmation by government officials of a planned terrorist attack at the Ernst Happel Stadium, we have no choice but to cancel the three planned shows for everyone's safety," organisers Barracuda Music said in a statement. "All tickets will be automatically refunded within the next 10 working days."

Earlier, Austria's General Director for Public Security, Franz Ruf, said a 19-year-old Austrian citizen had been arrested on Wednesday morning in Ternitz in the province of Lower Austria.

He also said a second arrest took place in Vienna in the afternoon, but offered no further details about the suspect.

“According to the current status of the investigation, the two suspects became radicalised via the internet,” Mr Ruf said. He also said the 19-year-old made an "oath of allegiance" to ISIS in July.

A massive police operation took place in Ternitz, where the suspect lived. A number of houses were evacuated while his home was searched. Mr Ruf commented that chemical substances had been found and were being examined.

Austrian Chancellor Karl Nehammer said in a post on X that the cancellations would be a "bitter disappointment for all fans" but that the situation had been "very serious".

"Thanks to the intensive cooperation of our police and [security agencies] with foreign services, the threat was recognized early, combated and a tragedy prevented."

The head of police in Vienna, Gerhard Pürstl, said 65,000 people per day had been expected to attend the concerts, as well as 22,000 fans outside the venue.

Investigations are ongoing.

Swift’s record-breaking Eras Tour began in Glendale, Arizona on March 2023, and has been extended several times. It has since passed through the United States, South America, Asia and Australia, and is currently on its European leg before it makes a return to North America.

In recent years, music performances and venues in Europe have become targets for mass attacks by Islamist militants.

In November 2015, ISIS gunmen attacked the Bataclan theater in Paris – part of an assault that hit other targets in the French capital – killing at least 130 people in total.

And in May 2017, the group claimed responsibility for a suicide bombing at an Ariana Grande concert in Manchester, England, that killed 22 people.

Swift herself has called these types of attacks her “biggest fear.”

In a 2019 essay for Elle Magazine, she wrote: “After the Manchester Arena bombing and the Vegas concert shooting, I was completely terrified to go on tour this time because I didn’t know how we were going to keep 3 million fans safe over seven months,” referring to the 2017 mass shooting at a Las Vegas music festival that killed 60 — the deadliest by a lone gunman in the US to date.

“There was a tremendous amount of planning, expense, and effort put into keeping my fans safe,” she wrote at the time, adding that those fears have carried over into her personal life – with the star carrying around emergency first-aid equipment like bandage dressing for gunshot or stab wounds.