DETECTIVES are investigating an armed robbery at the Co-op on Cross Lane, Bebington.

Officers were called to the shop at around 9.30pm on Wednesday after a man had entered the store, went into the manager's office and threatened him with what appeared to be a knife.

The manager was forced to put the takings into a bag.

The offender managed to leave the store with a substantial amount of cash before heading on foot on to Cross Lane.

He is described as 6ft tall and of slim build and was wearing a black tracksuit hooded top with a small white logo on the left breast and grey sleeves, and black tracksuit bottoms with a small white logo below the left knee.

The tracksuit bottoms were tucked into dark socks and white Reebok classic trainers. He was also wearing what appeared to be a homemade green wool balaclava.

Detective Inspector Dave Grisenthwaite said: "This is a particularly busy shop and we believe that there were a number of people in the store prior to this incident who may be able to help us with our enquiries.

"Although the staff were uninjured, this was a very distressing ordeal for them and we are asking for the assistance of the public to help us bring this offender to justice."

Anyone who witnessed anything or who has any information about this incident is asked to contact DC Angela Fling or DC Viv Trowell Birkenhead CID on 0151 777 2261, or Crimestoppers on 0800 555 111.