Republican dissidents are believed to be behind a car bomb in Northern Ireland which exploded hours before a controversial Orange Order march at Drumcree.

The explosion happened outside the Royal Ulster Constabulary station in Stewartstown, County Tyrone, 15 miles from Drumcree.

No-one was injured. The blast damaged the RUC station, businesses and a number of houses.

The Chief Constable of the RUC, Sir Ronnie Flanagan, has blamed the dissident republican group, the Real IRA, for the car bomb.

Speaking on the BBC's Breakfast with Frost, he said those responsible for the bomb were attacking the community.

The Real IRA was behind the Omagh bomb attack in 1998 in which 29 people died.

It opposes the IRA ceasefire and the peace process in Northern Ireland.

The Stewartstown bomb, which happened just before 0100 BST, came several hours before a march by Orangemen in Portadown, County Armagh, where the controversial Drumcree parade had been barred from the mainly nationalist Garvaghy Road.

The Secretary of State, Peter Mandelson, paid tribute to police officers who were clearing the area when the device exploded.

He said the bomb had been designed to heighten tension.

"The intention of the bombers was to inflame an already tense situation."

But Mid-Ulster Democratic Unionist Party assemblyman William McCrea said the Northern Ireland Secretary should put as much effort against the IRA as he did against the Orange Order.

Community relations in the mixed Protestant/Catholic village of Stewartstown are said by locals to be good.

The blast came after a week of loyalist protest at Drumcree and in other areas of the province after an Orange Order parade last Sunday was also barred from returning to their hall via the Garvaghy Road.

Eyewitnesses spoke of a "sheet of flame" pouring out of the car when it exploded. Windows of nearby houses were shattered.

The RUC said neighbours had noticed a car abandoned in the area at 2330 BST on Saturday.

Local people also said a masked man then left in another vehicle.

Many had thought the alert might have been a hoax, coming at the most sensitive period in the marching season.

Evacuation

The RUC began an evacuation of the area, after concern was raised by locals.

It is understood there was a telephone warning, but only after the evacuation process had started.

The explosion happened on the route of an Orange Order march and was heard 15 miles away at Drumcree.

The blast came on the sixth night of sporadic and violent protests - including the hijacking and burning of a bus in Carrickfergus, County Antrim.

Loyalist protestors at Drumcree lit a fire against army fortifications erected to block the road running across Drumcree Bridge towards the nationalist Garvaghy district.

Appeal for calm

Mr Blair's appeal for calm came on Saturday in a letter to the Portadown Orange Lodge, in which he said that he hoped that they would do everything to avoid "tension and violence - violence that can only rebound on the whole community in Portadown and Northern Ireland more generally".

But despite intense pressure, the Portadown District Lodge appealed to all Orangemen to stage a peaceful four-hour protest on Monday against the Parades Commission which rerouted the parade.

The lodge also called on its members who are MPs - the majority of whom are Ulster Unionists - to disrupt parliamentary business. Members at the Stormont Assembly should withdraw until "Orange rights are fully restored," it added.

But responding to criticism from Archbishop Robin Eames, the Church of Ireland Primate, the Orange Order stressed Sunday's protest would be peaceful.

It said that at the end of the service, only the lodge's district master Harold Gracey, lodge officers and members would parade to the police barriers and hand in a letter of protest.

Mr Gracey would then address the crowd before dismissing the parade - but, crucially, not ordering its members to disperse.

The protest will continue at the site, it says, until the Orangemen are allowed to return to their hall in the centre of Portadown via the "traditional" Garvaghy Road route.