One woman has been sent to hospital after a jewellery store robbery in broad daylight in downtown Hamilton Friday morning.

Police were called to Jewel Box Jewellers at the corner of King and James just before 10 a.m., police say. Three men broke into the shop and demanded money from the clerk, according to police Const. Debbie McGreal-Dinning. It's "believed" they had a gun, she said.

The three men grabbed some jewellery and took off, but police aren't yet sure in what direction, or if they had a vehicle. The woman behind the counter was taken to hospital with minor injuries, police say.

The police Break and Enter, Auto Theft and Robbery (BEAR) unit was on scene collecting evidence just after 11 a.m. McGreal-Dinning says a robbery such as this during the day isn't totally uncommon.

"We do have bank robberies that happen during daytime hours," she said. The investigation is ongoing.