A 19-year-old Islamic State sympathiser planned a suicide attack at a Taylor Swift concert in Vienna, the country's intelligence agency said on Thursday.

Austrian authorities detained two suspects on Wednesday for allegedly plotting to attack one of three Vienna concerts by the US star due to start Thursday. All were cancelled at the last minute leaving disconsolate "Swifties" to gather in the Austrian capital.

The 19-year-old main suspect had confessed, saying he "intended to carry out an attack using explosives and knives," domestic intelligence agency (DSN) head Omar Haijawi-Pirchner told a news conference.

"His aim was to kill himself and a large number of people during the concert, either today or tomorrow," he added. The concerts were to run from Thursday to Saturday.

The second suspect, a 17-year-old Austrian, was employed at a facility management company which would have "provided services" at the Ernst Happel Stadium where Swift was to perform, said Haijawi-Pirchner.

The younger suspect, who has so far refused to talk to authorities, was "in the area" of the stadium when he was detained, said Haijawi-Pirchner.

Chancellor Karl Nehammer said there were "concrete and detailed" plans to commit a "blood bath".

According to Interior Minister Gerhard Karner, a "tragedy was averted".

"The situation was very serious", he added, particularly in view of a recent attack at a Taylor Swift themed event in Britain, where three girls were killed in Great Britain.

Explosives and detonators were found in a search of the main suspect's apartment, authorities said.

Austria's top security chief Franz Ruf told reporters the two suspects had recently made changes in their private lives.

The main suspect, an Austrian with Northern Macedonian roots, had changed "his appearance and adapted it to Islamic State propaganda", while the second, an Austrian of Turkish or Croatian origin, had broken up with his girlfriend, he said.

Ruf earlier confirmed that authorities had received information "from foreign partners" which led to the arrests, but he declined to specify.

Police had promised to ramp up security for the concerts while having minimised any concrete danger, but organisers still cancelled Swift's shows. About 65,000 people were expected at each show.

Swift's fans gathered in parks and plazas across Vienna to share their disappointment. Dilyara Joldassova, a 23-year-old engineer who travelled from Kazakhstan for the show, said she was "broken-hearted".

Swift did not immediately comment on the decision to cancel the Vienna shows but after the British attack said she was "completely in shock".

Three girls were killed and five people seriously wounded in the mass stabbing at a dance class in Southport inspired by the American singer.

According to Ruf, police "did everything humanly possible to ensure" that the Vienna concerts "could go ahead", but the cancellation decision was taken by the organisers.

The 34-year-old star was to bring her record-breaking "Eras" Tour, which began its European leg in Paris in May, to Vienna on Thursday.

Following France, the tour stopped in Sweden, Portugal, Spain, the United Kingdom, Ireland, the Netherlands, Switzerland, Italy, Germany and Poland.

By the end of last year, "Eras" had already become the first tour to sell more than US$1 billion in tickets and it's on track to more than double that by the time it concludes in Vancouver in December. (AFP)