A gang of armed robbers has pleaded guilty to a series of raids on stores.

The five-strong group admitted conspiring to commit a series of robberies across the Midlands.

On January 23 last year, four men wearing balaclavas and one brandishing a sawn-off shotgun ambushed staff at the Co-op in the Westgate Centre, Chipping Norton.

The 13 employees were held hostage for up to an hour-and-a-half until help arrived.

The men fled on motorbikes with cash from the safe. The Co-op would not confirm the amount stolen, but weekend takings were thought to be about £30,000.

In a raid on the Tesco Express store in Eynsham on February 18 last year, four robbers wearing balaclavas forced their way in between 5.30am and 6am, and pushed four members of staff into a back room.

The robbers tied them up and demanded information about the shop's safe, before taking thousands of pounds.

One male member of staff was kicked in the head and had to be taken to Oxford's John Radcliffe Hospital. His injuries were not serious.

The raids were two of 11 armed robberies.

At Nottingham Crown Court, Richard Kavanagh, 31, David Bracken, 27, and Sean Reilly, 24, all from Coventry, pleaded guilty to conspiracy to commit armed robbery between October 2005 and April last year.

Co-accused Daniel Bracken, 29, also from Coventry, previously admitted a number of robberies. Darren Summerfield, 32, previously pleaded guilty to driving offences and a number of robberies.

Kavanagh admitted conspiracy to commit robberies on the basis that he was involved only from January 27, 2006.

Reilly admitted the same charge on the basis he was involved in only two raids.

The defendants were remanded in custody until sentencing.