British police hunting a gang of armed robbers who shot dead one female police officer and seriously injured another in the northern city of Bradford arrested three men in connection with the case today.
The men were arrested in London.
Police had earlier arrested a man and a woman in the capital this morning and all five are being held in custody.
The two women officers were shot as they responded to an alarm at a travel agency in the centre of the northern city of Bradford on Friday afternoon.
One female officer, Sharon Beshenivsky, 38, a mother of three children and two step children, was shot dead and another, Teresa Milburn, 37, was shot in the shoulder.
Milburn is under armed guard in hospital.
Both women were relatively inexperienced and Beshenivsky had only been in the job since February this year.
But the police said it was not unusual to have two such officers working together.
The murder, which was carried on the front pages of nearly all Britain's newspaper front pages and drew comment from Prime Minister Tony Blair and Home Secretary Charles Clarke, also prompted the question of whether the police should be armed.
British police do not normally carry firearms although small specialist units do.
Police told a news conference earlier on Saturday they were looking for three men, one Asian and two black, who were between 20 and 30 years old.
"More than one of these men was armed with a fire arm and one of them had a knife," Detective Superintendent Andy Brennan said.
A police spokeswoman said extra officers had been drafted in to work on the case.