Police have launched an international manhunt for an "extremely dangerous" murder suspect who escaped from a prison van after it was ambushed by three masked men armed with sledgehammers.

John Anslow was sprung from custody after a "well-orchestrated armed ambush" and must be found quickly, Justice Secretary Kenneth Clarke said.

The gang stopped the van, smashed its windows and punched its driver as it was transferring inmates from prison to court this morning.

Detectives said Anslow, who was charged with the murder of businessman Richard Deakin last week and upgraded to a category A prisoner, was "extremely dangerous" and should not be approached by the public.

Three men, including two armed with sledgehammers, used a silver Volkswagen Scirocco to stop the prison van at about 8.20am, shortly after it left Hewell prison in Redditch.

The guards were threatened with a blade, sources said, and Anslow, who was being taken to Stafford Crown Court where his case was listed for a preliminary hearing, escaped.

Police believe the gang then switched to a silver Mercedes car, with the partial registration KR11, in Stoney Lane, Bromsgrove, soon after the attack in Hewell Lane, Tardebigge.

Mr Clarke said: "This was a serious criminal incident involving a well-orchestrated armed ambush.

"The first priority is to ensure that this man is quickly found and arrested."

He added that he has also ordered a full inquiry into the security categorisation and management of the prisoner "so that we can learn lessons for the future".

Anslow was classed as category A, a grade reserved for those prisoners whose escape would be highly dangerous to the public, police or security, and for whom the aim is to make escape impossible.

Detective Superintendent Martin Evans, of Staffordshire Police which is leading the hunt, said Anslow, who was also known as Skitz, has strong connections across the country, including London, as well as overseas.

Officers were working with all forces, the UK Border Agency (UKBA), and authorities in other countries to track him down, and all airports and railway stations were being alerted.

Detective Inspector Jon Marsden, of West Mercia Police, added that Anslow was one of five men charged with the murder of Mr Deakin, who was shot dead in Chasetown, Staffordshire, in 2010.

Mr Deakin, 27, died after being shot while alone at his home in Meadway Street, Chasetown, Staffordshire, at about 8.30am on July 5 2010.

Police launched various appeals for information following his death, including a feature on the BBC's Crimewatch programme, and a £20,000 reward was offered for information about his killing.

His family were described as "shocked" by officers today.

Prisoner escort firm GEO Amey confirmed that two of its staff were treated by paramedics at the scene of the attack after both were threatened by the gang and one suffered facial injuries.

Two other prisoners who were also in the van were not released.

A police helicopter could be seen circling above the area as officers from the West Midlands and Staffordshire joined the manhunt.

Hewell prison houses more than 1,400 inmates across three blocks holding category B, C and D prisoners.