A SUSPECTED gunman was arrested at St Paul's Cathedral today.

London City Police swooped on the man, arresting him in the ground of the capital's landmark just after midday.

A spokesperson confirmed the man was believed to be in possession of a firearm.

They said: "We can confirm we've arrested a man who we believe to be in possession of a firearm at 12.05 today.

"He was detained behind One New Change by armed officers.

"There is no indication this incident is terror-related at this time."

One witness tweeted; "I witnessed this engagement by our truly professional #CityPolice as I exited @STPaulsLondon after the #GuildsService so proud of men & women in uniform keeping London Safe."

Armed police were pictured at the scene as tourists flocked outside.

Forensic officers were later seen examining the scene.

St Paul's Cathedral has been contacted for comment.