A deafening bang and a burst of flame in front of the Dolce & Gabbana boutique in Vienna's 1st district caused alarm on Monday afternoon - it is believed the explosion was caused by a faulty power line.

Paving stones flew into the air and one woman is reported to have been knocked out of her chair at a nearby cafe by the powerful explosion.

"Two people pulled the lady up and then ran off,” a witness told the Kronen Zeitung newspaper.

A short while later police arrived and ordered that the designer shop on Wallnerstrasse be evacuated. Employees and customers took refuge in nearby Michaelerplatz.  

A large part of the Wallnerstrasse had to be cordoned off, and surrounding shops were closed.