With their faces hidden by homemade masks, these two robbers are caught on camera holding up two service stations at knifepoint.

The images - showing the pair as they hit the service stations in the early hours of Monday and Tuesday in Faringdon and Frilford Heath - were released by police yesterday, on the day figures confirmed a jump in violent crime across Oxfordshire.

In both cases the robbers threatened staff with a knife before fleeing with cash. Detectives believe the robberies were almost certainly committed by the same two men.

In the first raid, the pair forced open a till at the Acorn Service Station, Park Road, Faringdon, at 1.55am on Monday.

The raiders placed a bin between the automatic doors and went behind the counter to open a till, before being challenged by a worker.

Police spokesman Tim Wiseman said: "One of the males showed that he had a knife with him and demanded money. A locked strong box was opened and further cash taken."

They stole about £500, while the worker was left uninjured.

Twenty-four hours later, Frilford Service Station, in Frilford Heath, was hit. The robbers forced open the automatic doors and used a holder for shopping baskets to stop them closing.

After demanding money at knifepoint, they took about £85 from the till and 30 packets of cigarettes.

Manager Sarah Rashid said: "The cashier had a slight cut on his hand and was shaken, but was back at work straight away."

Dc John Ablett, of Abingdon CID, said: "Both incidents involved sudden and very frightening attacks. We have excellent CCTV images of both incidents and we strongly believe that both are linked.

"I hope that by releasing the images I may hear from someone with information.

"I would like to ask anyone who was in these areas around the time of the raids to consider if they saw anything suspicious, particularly any vehicles.

"I also hope that by demonstrating how frightening these incidents were, someone out there who may know who is responsible will get in touch."

Anyone with information can contact police on 08458 505505 or Crimestoppers on 0800 555111.

FIGURES REVEAL RISE IN SEX CRIME

SEX offences have risen by 23 per cent in Oxfordshire over the last year, Home Office statistics reveal today.

This week alone the Oxford Mail has reported three street sex attacks in Oxfordshire.

Two involved 15-year-old girls attacked by men in Oxford, and another involved an 18-year-old woman assaulted by a taxi driver.

Violence against the person has also increased by nine per cent and robbery by 18 per cent, while burglary has fallen three per cent, theft of a vehicle has gone down 16 per cent and theft from a vehicle has dropped eight per cent.

Oxfordshire police commander Chief Supt David McWhirter said: "The reductions in vehicle crime, burglary and theft are substantial and I want to ensure that this downward trend continues. We will keep the pressure on with street crime and continue our efforts against robbery."

Nationally, total recorded crime has gone down one per cent, burglary has gone down seven per cent, vehicle crime is down by three per cent and robbery has risen by eight per cent.