Lady Gaga used a tricolor flag during her routine on Saturday night at Belfast's Oddessy arena much to the dismay of her fans.

Up to 10,000 revelers packed the arena for the Poker Face star's Halloween show, which was one of three Gaga was performing in Northern Ireland as part of her Monster Ball Tour.

However when the award winning pop star pulled out a Republic of Ireland’s green, white and orange flag during the show, fans were none too impressed.

One fan said a lot of audience members were uneasy: “A lot of people were not impressed and there was a bit of unease in the crowd.

“Some people were making comments and others challenging them,” she told the Belfast Telegraph.

“It didn’t spill over but I certainly think the atmosphere suffered after that as a result.”

Another fan said: “I just felt it was inappropriate, but maybe she didn’t realise Northern Ireland is separate from the Republic.”

Gaga made no reference to the flag during her performance but instead used it as a prop.

Silly Gaga, check your geography before whipping out flags!