A gunman believed to have carried out two armed robberies on buses has struck again.

The man got in the back of a taxi in Borrowmead Road, Northway, at about 9.50pm yesterday.

He pulled a metal chain around the driver’s neck from behind, forcing him to hand over cash and a palm-top computer.

He then hit him over the head with a gun and ran off in the direction of Maltfield Road.

Police believe he is the man who raided two buses this week.

He is described as white or Asian and in his 20s.

Taxi and bus drivers have been warned not to let any passengers inside if they have their faces covered.

The gunman first struck on an Arriva 280 bus in London Road, Wheatley, at about 9.40pm on Wednesday, stealing £120.

At about 3.30am on Thursday, he attacked the driver of an Oxford Tube bus, stealing cash and hitting him on the head with a handgun.

Anyone with information should call police on 08458 505505 or the anonymous Crimestoppers hotline on 0800 555111.