An 18-year-old Iraqi national suspected of having links to a terror plot on a Taylor Swift concert has been detained in Austrian capital Vienna.

Police swooped on an address in the city this morning, making the second arrest as part of an investigation into the plot - which could have seen some 20,000 fans targeted outside Vienna's Ernst Happel Stadium.

The Iraqi national is said to have come from the same circle as the main suspect, a 19-year-old Austrian with North Macedonian roots, according to Austria's interior ministry.

Both today's detainee and the 19-year-old suspect had sworn loyalty to infamous terror group Isis.

Officials insisted today's arrest wouldn't be the end of investigations, with more suspects set to be questioned and properties searched as the terror probe continues.

All three Vienna concerts of Swift's Eras Tour, slated for Thursday, Friday and Saturday, had been called off late on Wednesday after the deadly plans were uncovered.

And two other Austrian youths, aged 17 and 15, were detained on Wednesday over the reported plot.

The 15-year-old has been released and is being treated as a witness, Austria's Kurier newspaper reported on Friday.

The Iraqi suspect is reported to have sworn allegiance to Isis on August 6 - but it remains unclear whether he had anything to do with the planned attack, the outlet added.

More to follow...