A group of Gisborne grandma's fought off a pair of wannabe thieves after they disturbed Friday night bingo

The 30 women - the oldest of whom was 87 - were at the Gisborne Pirates Rugby Club at 8pm when two men in masks burst in on their game.

But the pair realised they were outmatched... after a 67-year-old nana flipped a table on one - to defend their 700-dollar prize pouch.

She says the man fell on the ground - and the group began berating him with handbags and chairs until he ran off.

Rugby club president Jenny Akurangi says she's amazed the nannies returned to their game, once the police and their dogs left to chase the thugs.

A police investigation is underway.