The suspect targeted a jewellery shop at around 4.50pm on Tuesday, leaving two employees with minor injuries.
A manhunt was launched after he made his escape on foot.
Police have advised motorists to abstain from offering lifts to strangers. Any suspicious activity should be reported to 113.
According to a description released by police on Tuesday evening, the perpetrator was around 1.80 metres tall, white, of average build, with close-shaved dark hair and heavy stubble. He was said to be around 60 years old and wore glasses and grey clothing. Witnesses said he spoke German and French, and was missing his lower teeth.
Anyone with information on the suspect should contact the police as a matter of urgency.
