FOUR masked armed robbers escaped with a large amount of cash after holding up a security van outside an Oxford bank today.

The gang ambushed two security guards as they arrived at the Abbey bank in Banbury Road, Summertown at 5.30am today, and escaped with a substantial amount of money.

One of the guards, who work for G4S (also known as Group 4 Securicor) was injured in the attack and has been taken to hospital. He suffered a head injury, which police said was not thought to be serious.

Acting Det Insp Kevin Elkins said: "We believe the offenders made off in a white Corsa van towards Woodstock Road, and I appeal for anyone who saw that vehicle or anything else suspicious around that time to contact me immediately.

"The men were armed with what is believed to be hand guns, but no shots were fired."

The four men had their faces covered. Police said one was black and the other three were white.

If you have information please contact Acting Det Insp Elkins via 0845 8 505 505. If you do not wish to speak to police or give your name you can call the Crimestoppers charity anonymously on 0800 555 111.

The raid follows a similar attack on the Abbey bank, in the Bury Street precinct, Abingdon, just over two weeks ago, but there has been no formal linking of the robberies.

Detectives have cordoned off the shopping parade where the bank is and are speaking to witnesses.

There is no description yet of the robbers nor any vehicle they may have used.

However officers have removed a blue Vauxhall Corsa and a silver Mercedes from the scene.

Shortly before 9am, staff from the Abbey arrived to get into the branch but had to wait outside while police continued their investigation.

Police removed the cordon which had been set up around the bank at about 11.15am.