Taylor Swift shows in Vienna canceled after 2 arrested for planning ...

Taylor Swift's three concerts in Vienna this week have been canceled after two suspects were arrested for allegedly plotting a terror attack, authorities said.

"We have no choice but to cancel the three scheduled shows for everyone's safety," a message from Barracuda Music said. "All tickets will be automatically refunded."

The cancellation comes hours after authorities announced a 19-year-old Austrian citizen was arrested Wednesday morning and a second suspect was arrested in the afternoon.

The suspects allegedly radicalized themselves online, Franz Ruf, director-general for public safety in the Ministry of the Interior, said at a press conference. The 19-year-old suspect allegedly pledged allegiance to the leader of the Islamic State at the beginning of July, Ruf said.

Vienna was a target of their planned attack and the 19-year-old suspect had a particular focus on Swift's Vienna concert, Ruf said.

The pop star had concerts scheduled in Vienna this Thursday, Friday and Saturday.

Information about the threat to the tour dates originated with U.S. intelligence and was passed to the Austrians and Europol, multiple law enforcement and intelligence sources told ABC News.

Though inspired by ISIS, the sources said investigators do not believe the alleged plot was directed by ISIS operatives.

U.S. intelligence found at least one of the suspects pledged to ISIS-K on the messaging app, Telegram, in early July, the sources said.

Investigators are not convinced that the alleged plot would have worked and they do not know if a functioning bomb was produced. However, Viennese investigators did find explosive precursor chemicals which showed a degree of motivation and planning, sources told ABC News.

Before the shows were canceled, Ruf said security at the concerts would be increased. The shows were expected to draw 65,000 concertgoers per day, with an additional 10,000 to 15,000 fans outside of the area, police said.

Swift kicked off the massively successful "Eras Tour" in Glendale, Arizona, on March 18, 2023.

Investigators in Austria are looking at surveillance footage to determine whether one or more of the suspects had previously visited the concert site for reconnaissance or if they had visited other potential targets.

As ABC News has previously reported, law enforcement officials have been concerned about mass gathering attacks since the deadly Moscow concert hall assault earlier this year for which ISIS-K claimed credit.

In October 2023, the pop star released a concert film chronicling the record-breaking tour, "Taylor Swift: The Eras Tour," that went on to break records of its own and earn a Golden Globe nomination.

At the 100th stop of the tour this summer in Liverpool, England, the 14-time Grammy winner told the audience the tour "has definitely been the most exhausting, all-encompassing, but most joyful, most rewarding, most wonderful thing that has ever happened in my life thus far."

The Eras Tour will end in Vancouver, Canada, on Dec. 8.

ABC News' Carson Blackwelder contributed to this report.