The force, which also yesterday issued descriptions of three people wanted for questioning in connection with last Thursday's IRA bomb attack in the city, announced the move following a meeting of senior officers. Other forces may follow suit.
Chief Superintendent Tim Moran, divisional commander of the city centre, said vehicles would only be stopped if they fitted intelligence profiles: 'It is not a random check of vehicles. They are being selected for being stopped and searched.'
He added: 'It is regrettable we have been forced to the situation where we have to take on board this type of policing operation. But in the light of events in recent years it was perhaps predictable.'
Mr Moran said the operation was open-ended and would be carried out every day throughout the area. Like the Metropolitan Police, Greater Manchester stressed that the operation was partially an attempt to reassure the public that the police were taking action.
Until last Thursday's explosions, Manchester had not been attacked by the IRA since late 1991. Previous incidents had been confined to firebombs in stores.
Road-blocks, which have been criticised by civil liberties groups, have to be authorised under the Police and Criminal Evidence Act by an officer of at least superintendent rank. They can only be in relation to specific crimes and within a defined area, although there is room for interpretation of the provisions.
Police have powers to stop any vehicle, but can only search if they have reason to be suspicious; these reasons can include the type of vehicle or the refusal of the occupant to allow a search.
Earlier yesterday, police issued descriptions of three people they want to trace in connection with last Thursday's explosions, which injured 64 people. Two of them were men spotted near the scene of the first bombing in Parsonage Gardens.
One, a man in his twenties, wearing jeans and an anorak, was picked up by a blue car at 3.15am - five and a half hours before the explosion. The other was a youth, aged 16 or 17, seen near the shrubbery in Parsonage Gardens at 7.40am, an hour before the blast. Police also said they were anxious to find a man in a green anorak who was seen running from the site of the second bomb an hour before the blast.
Greater Manchester Police also said yesterday that they believed the bomb warning which led to the closure of Piccadilly railway station in the city for six hours on Sunday was a genuine hoax call from the IRA. A recognised codeword was used.
Tern Hill Barracks in Shropshire, the scene of an IRA bomb in 1989, was placed on high alert yesterday after a sentry spotted intruders.
The Royal Ulster Constabulary warned that cars left parked in certain areas of Belfast and towns throughout Northern Ireland could be blown up.
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