The ISIS teen who plotted a terror attack on a Taylor Swift concert has been pictured for the first time as neighbours say he completely changed his look recently. 

The 19-year-old ISIS fanatic has been identified as Beran A., who lived in a newly-built end-terraced house in Ternitz, nearly 50 miles south of Vienna, where he spent his childhood.

A few years ago, Beran A.'s parents - who immigrated to Austria from North Macedonia - moved into a new-built house in the Neunkirchen district of Ternitz with him and his younger sister. 

Ternitz residents told local media that he used to be a 'harmless boy next door' in jeans and sneakers, who was born in Austria and attended a local school. 

But Beran A. had changed recently, according to his neighbours, coinciding with his pledge of allegiance to ISIS in early July. He grew a long beard and was often spotted wearing a long-sleeved cotton shirt, with a new picture of him showing him posing with huge zombie knives and an ISIS flag.

The 19-year-old was arrested in Ternitz, south of Vienna, Wednesday morning while a second teen, aged 17, was detained in the Austrian capital in the afternoon, according to director-general for public safety Franz Ruf. The two inhaled laughing gas before planning their terror acts, according to Heute. 

Taylor Swift was due to perform in front of an estimated 170,000 fans on August 8, 9, and 10 at Vienna's Ernst-Happel-Stadion, but the shows were cancelled last night.

Beran A. and his accomplice had planned to attack Swift's concert venue by driving into the crowd outside at 4pm today before attacking them with knives and machetes and detonating a suicide bomb.