A nursery in Austria had to be evacuated after a World War II grenade was found inside a tree at the school's playground.

The nursery boss was the first one to discover the historic weapon after he saw it wedged in a tree in the garden.

After calling for help, an explosives expert from the police came to the school and confirmed it was an unexploded hand grenade.

Police then called the army bomb disposal unit, which evacuated the school and surrounding areas of the Hietzing district in Vienna.

The hand grenade, which was partially embedded in the tree, was dislodged and taken away by bomb experts.

Police spokesperson Markus Dittrich told local media the children were never in danger.

"The children were not in any danger at any time.

"The nursery school was evacuated while the bomb disposal experts removed the hand grenade."

It is not known how long the grenade had been there or how it ended up in the tree.

Vienna was bombed more than 50 times during WWII.