A large firebomb in a stolen van has been destroyed close to the route of the Orange Order's main parade in Belfast.

It came as tight security was being put in place for 12 July, the main day in the Protestant Orange marching season.

Tens of thousands of people are taking part in celebrations by loyal orders which commemorate William of Orange's 1690 Battle of the Boyne victory over Catholic King James II.

Army explosives experts blew up a van containing a detonator and a large amount of petrol in the early hours of Friday.

Security sources linked the device to dissident republicans who are opposed to the Northern Ireland peace process.

The intention is to organise a major riot and put these people in conflict with the police and Army

Assistant Chief Constable Alan McQuillan

Two controlled explosions were carried out following a telephone warning to police about the van in Little Donegall Street just before midnight.

Belfast Ulster Unionist councillor Jim Rodgers said he believed the device was intended to kill Orangemen, bandsmen and spectators at Friday's parade in the city.

'Conflict'

Earlier, police chiefs claimed that republican paramilitaries were planning to bus youths into Ardoyne to riot in protest against a disputed Orange parade through the area.

Speaking about the possible rioting, Assistant Chief Constable Alan McQuillan said: "The intention is to organise a major riot and put these people in conflict with the police and Army."

He appealed to Sinn Fein leaders to hold a peaceful and legitimate protest.

But Sinn Fein North Belfast assembly member Gerry Kelly said there were no plans by republicans to start trouble.

Gerry Kelly: No plans for trouble

"What I have said to the residents here who are organising this protest is that there is a trap being set, by Alan McQuillan in particular.

"If he has all the evidence then let him produce it," said Mr Kelly.

The morning parade passed Ardoyne without incident.

Serious clashes followed the return of the parade on the evening of 12 July last year.

Appeal for restraint

There was also a large security presence in the Springfield Road area of west Belfast as Orangemen set out on their annual Twelfth march.

On Thursday, attempts by Sinn Fein to have the two march routes reviewed were rejected by the Parades Commission which urged all sides to show restraint.

Ulster Unionist leader David Trimble urged loyalists not to fall into any traps laid by republicans.

Deputy First Minister Mark Durkan said people should be "measured and mature in how they conduct themselves".

Belfast Lord Mayor Alex Maskey appealed for calm ahead of the Twelfth marches.

North Belfast Democratic Unionist MP Nigel Dodds met police chiefs on Thursday to seek assurances about security surrounding marches.