Bomb experts have been called to a Wellington backyard where a possible grenade has been found.

Police and New Zealand Defence Force bomb experts were called about 1.30pm today to examine what is thought to be a grenade in a Mount Cook backyard.

At this stage bomb experts were unsure whether it was a grenade, said police duty Inspector Chris Tate.

Residents and neighbours were not in any danger if they kept their distance as grenades had a limited range of around eight metres, said Mr Tate.

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"The only danger is if someone is playing with it."