Austrian security officials say a 19-year-old arrested on Wednesday was planning to kill "a large crowd of people" in a suicide attack at a Taylor Swift concert in Vienna.

Officials say the teen - who had previously pledged allegiance to the Islamic State group (IS) - confessed that he "intended to carry out an attack using explosives and knives".

Swift's three sold-out shows at the Ernst Happel Stadium have been cancelled. More than 195,000 people had been expected to attend.

Local media have also reported that the 19-year-old, the main suspect out of three, had stolen chemicals from his former workplace.

The Kurier newspaper, citing sources, reported that he used to work at a metal processing company in his home town of Ternitz, and that he had made progress in building a bomb.

The outlet also reported that he had planned to drive a car into the crowd expected to gather outside the stadium.

Security officials at a news conference on Thursday did not comment on where he got the chemicals, but public security chief Franz Ruf told reporters that chemical substances and technical devices found at the main suspect's house showed "concrete preparatory actions".

The head of Austria's Directorate for Protection of the State and Intelligence (DSN) Omar Haijawi-Pirchner, said weapons were seized from the main suspect's house, and that "his aim was to kill himself and a large crowd of people either today or tomorrow at the concert".

Mr Ruf added the teen had posted a video online confessing to the plot, quit his job at the end of last month and told people that he had "big plans".

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They also revealed that the main suspect - an Austrian citizen who was born there but who had North Macedonian parents - had recently changed his appearance and "adapted it to Islamic State propaganda", and had been consuming and sharing Islamist propaganda online.

A second suspect - a 17-year-old Austrian of Turkish or Croatian heritage - was employed at a company which would have "provided services" at the stadium where Swift was to perform.

A 15-year-old suspect has so far refused to talk to the authorities, and was "in the area" of the stadium when he was arrested.

Officials added that they were not looking for any other suspects.

Also at the press briefing was Interior Minister Gerhard Karner who said "a tragedy was averted", and the attack was foiled with the help of international intelligence as Austrian law does not allow censorship of messenger applications.

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"The terrorist threat has intensified throughout Europe and Austria was and is no exception," he said, adding that major concerts are "often a favourite target of Islamist attackers".

Coldplay are due to perform seven concerts in Vienna from 21 August as part of their Spheres World Tour.

Mr Haijawi-Pirchner said there was no information suggesting a specific threat to upcoming events in Austria, but security measures remain high.

Swift's Vienna concerts were part of the European leg of her Eras Tour, which began in Paris in May.

The tour has made stops in a number of countries including Sweden, the UK, Ireland, the Netherlands, Italy, Germany and Poland.

Swift is set to head to London to perform five shows at Wembley Stadium next week.

UK policing minister Diana Johnson said Scotland Yard would look at intelligence ahead of the Wembley Stadium dates.

London Mayor Sadiq Khan has told Sky News that the city will "carry on" and that the police will work with City Hall and councils to ensure the concerts take place safely. (BBC)

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