A ninth suspect has been arrested by police investigating an alleged Iraq-style kidnapping and beheading plot in the UK.

It follows the detention of eight people at addresses in Birmingham early today.

Assistant Chief Constable David Shaw, of West Midlands Police, revealed the last suspect was stopped on a motorway near the city.

He said officers were carrying out a "very, very major investigation" that would take "days if not weeks" to complete.

It has been reported the alleged plotters intended to post a video of the hostage being tortured and killed on the internet.

The target was a British Muslim soldier in his twenties who is now under police protection.

The soldier, who has not been named, has served with UK forces in Afghanistan.

His abduction would have mirrored the kidnappings of the British hostages Ken Bigley and Margaret Hassan by Iraqi insurgents.

The suspects - believed to be of Pakistani origin - were detained under the Terrorism Act after a six-month surveillance operation.

Police press conference It is thought they are being held in Coventry. Two are said to be males aged 31 and 29.

The latter has been named locally as Amjad Mahmood.

Sky's Crime Correspondent Martin Brunt said officers feared the alleged plot was "coming to fruition".

The fact the aim was apparently not to cause mass casualties, as in previous terror attacks, signalled a "chilling" change in tactics.

The suspects had been tracked in a combined police operation led by the Midlands Counter Terrorism Unit.

They were supported by officers from the West Midlands police and the Metropolitan Police.

Officers swooped on 12 addresses in the Sparkhill, Washwood Heath, Kingstanding and Edgbaston areas of Birmingham at 4am.

Police said eight people were held "on suspicion of the commission, preparation or instigation of acts of terrorism under the Terrorism Act 2000.

"Twelve addresses have been secured and sealed off... and all are currently being searched."

The statement warned: "We are mindful that communities, locations or individuals don't become a target as a result of recent events.

"Hate crime will not be tolerated and we will take robust action where necessary."

A Home Office spokesman said: "This operation is a reminder of the real and serious nature of the terrorist threat we face."

Today's arrests come after police detained a total of five people in anti-terror raids in Manchester and Halifax, West Yorkshire, last week.