A mysterious cloud engulfed Venice's iconic Saint Mark's Basilica, in what appeared to be a fire, but turned out to be all smoke.

Thieves attempted to rob the Missiaglia jewellery shop, which claims to be the city's oldest, in broad daylight in San Marco square in Venice on 17 March.

The robbers apparently changed their mind when they saw a heavy police presence in the area and ran away, lighting a smoke bomb near to cover their traces.

According to police, there were at least two people involved who fled the scene by mingling in the crowd of tourists enjoying the sights.

Panic spread among tourists following the smoke bomb, but no one was injured, the Italian news agency Ansa reported.

Various police forces who regularly patrol the square in counter-terrorism operations, are interrogating witnesses to gather information about the thieves and whether they were armed.

CCTV footage in the are is also being examined as the authorities cordoned off the area around Saint Mark's Basilica to recover the smoke bomb remnants.