Organisers called off three Taylor Swift concerts in Austria following the arrest of two suspects accused of planning a terror attack during the Vienna stop of her Eras tour.

This unprecedented move, potentially costly for Vienna's businesses, has left fans devastated and highlighted the vulnerability of large concerts to terrorist attacks and spree killings.

Swift was set to perform three concerts in the European city from Thursday to Saturday, but all have been cancelled, according to her Austrian concert promoter, Barracuda Music.

Barracuda Music announced online yesterday, "With confirmation from government officials of a planned terrorist attack at Ernst Happel Stadium, we have no choice but to cancel the three scheduled shows for everyone's safety."

At a press conference in the capital, police reported that a 19-year-old Austrian national, identified as an ISIS sympathiser, was apprehended on Wednesday morning in Ternitz, Lower Austria. Additionally, another arrest was made later in Vienna, as per CNN.

According to police, the individuals had been "radicalised through the internet," with the 19-year-old having pledged allegiance to the ISIS leader in July.

Authorities stated that the two suspects had taken "concrete preparatory measures" for a terrorist attack, following police suspicions that explosives were being kept at the residence of the suspect in Ternitz.

According to the Associated Press, police also reported that chemical substances were found at the 19-year-old's residence and are currently being analysed.

Barracuda Music stated that refunds for all tickets to the cancelled events will be processed automatically within the next 10 business days.

Authorities estimated that approximately 65,000 attendees were anticipated for each of Swift's shows in Vienna, with an additional 15,000 to 20,000 fans expected to gather outside the stadium.

In recent years, music events and venues across Europe have become targets for large-scale attacks by Islamist extremists.

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In November 2015, ISIS gunmen launched an assault on the Bataclan (theatre) in Paris, among other sites in the city, resulting in the deaths of at least 130 people.

Additionally, in May 2017, the group took responsibility for a suicide bombing at an Ariana Grande concert in Manchester, England, which killed 22 individuals.