A third teenager has been arrested in connection with a foiled attack on now-cancelled Taylor Swift concerts in Vienna.

Austrian interior minister Gerhard Karner said the 18-year-old was taken into custody after allegedly being in contact with the main suspect.

Mr Karner announced the arrest during an unrelated news conference on Friday.

Investigators are scrutinising the “networks” of the suspects, the Austrian interior ministry said, adding in a statement that investigators have turned to evaluating physical and electronic evidence.

Many of them had spent thousands of euro on travel and lodging in Austria’s expensive capital city to attend the Eras Tour shows at the Ernst Happel Stadium.

The 19-year-old main suspect and a 17-year-old were arrested on Tuesday, while a 15-year-old was also interrogated but was not arrested.

Authorities say the plot appeared to be inspired by the so-called Islamic State group (IS) and al-Qaida, and that the third suspect had taken an oath of allegiance to IS.

Investigators found bomb-making materials at one of the suspects’ homes.

A suspect has also confessed to planning to “kill as many people as possible outside the concert venue”, according to authorities.

Officials say the main suspect and the 18-year-old arrested on Friday both pledged “oaths of allegiance” to IS.

Three sold-out concerts were cancelled on Wednesday because of the plot, devastating Swifties from across the globe.