South Wales Police says it is responding to "an incident" on Cowbridge Road East in Cardiff with armed officers.
Police were called out just before 4pm on Monday. Eyewitnesses say the officers went into the Lloyd's Bank.
A South Wales Police spokesperson told ITV News, "firearms officers were deployed to the area to ensure the safety of the public and officers at the scene."
A police helicopter was also seen circling the area.
The incident is ongoing.
More top news
There'll be clear spells overnight with mist inland. But tomorrow it's all change with scattered showers!
Described as the 'hidden disability', autism affects how people perceive the world and interact with others.
A driver from Newport has been handed a 21 month sentence behind bars after wracking up a number of driving offences.