Vienna - An earth tremor recorded by the meteorological institute in the Austrian capital turned out be a detonation from an unexploded World War II bomb, police said Saturday.

The cause of Friday evening's tremor in the suburb of Liesing was discovered the following morning by a gardner, who found a huge crater in a field a few hundred metres from the home of his employer.

Police said a 500-kilogramme bomb dropped from a plane more than 63 years ago had buried itself deep in the earth and remained undetected until its acid fuse triggered the blast, which caused only minimal damage. (dpa)