A pair of masked robbers made off with more than £10,000 from G4S security guards after an armed raid at a bank.

The men, armed with weapons and wearing blue overalls and masks, smashed their way into a Santander bank in Argyll in the early hours of Wednesday.

The G4S guards were inside the branch on West Princes Street in Helensburgh to transfer cash at around 12.30am when the men entered and threatened them with weapons. They then made off in an unknown direction with the cash box, which contained a five-figure sum of money.

The suspects are described as being of medium height, medium build and were wearing blue overalls and masks at the time of the incident.

Detective inspector Douglas Wilson, of Argyll and West Dunbartonshire CID, said: "Our inquiries are at an early stage following this calculated robbery of a cash box in West Princes Street.

"The employees were placed in a state of fear and alarm as two men entered the premises of the bank, threatened the men with weapons and then made off with the cash box in an unknown direction.

"A substantial investigation is under way to trace the men responsible. A dedicated team based at Helensburgh police office is currently analysing any available CCTV.

"Officers remain at the scene on West Princes Street and local door-to-door inquiries are currently being progressed.

"At this time we are seeking the assistance of the public to come forward with any information which could help our investigation.

"It is possible that someone has seen or heard a disturbance at the Santander bank on West Princes Street.

"You may have seen men running off from the scene or heard the sound of cars travelling at speed.

"You may not think the information you have is valuable to us but any information can make a real difference.

"As part of our larger investigation, your assistance could be critical in tracing the persons responsible."

Anyone with information is asked to contact officers at Helensburgh police office via 101.

Alternatively, please call Crimestoppers on 0800 555111 where information can be given anonymously.