Belfast's most senior police officer has said republicans are planning a large scale riot in the Ardoyne area of north Belfast on Friday.

A disputed Protestant Orange Order parade is due to take place in the area as part of the annual 12th of July loyal order celebrations.

The police said they have information that petrol bombs and acid bombs are being prepared.

We are saying that a republican paramilitary organisation is clearly organising and is directly behind this

Alan McQuillan PSNI

Assistant Chief Constable Alan McQuillan said: "We have very clear information that large numbers of republican youths are being bussed into the area by republican paramilitaries and that large quantities of petrol bombs and acid bombs are being manufactured.

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

The leading officer appealed to Sinn Fein leaders to hold a peaceful and legitimate protest.

He added: "We are saying that a republican paramilitary organisation is clearly organising and is directly behind this."

While he said he was not going to be specific about which group was behind it, Mr McQuillan said the IRA was the major paramilitary organisation in Ardoyne.

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

He said Mr McQuillan's warning placed the onus on the prime minister to rule on the IRA ceasefire before Westminster rose for the summer.

"Loyalists must let republicans by their own actions give Tony Blair no choice over what he has to do by July 24 in London," he said.

Serious disturbances

On Thursday, the Parades Commission rejected a request from Sinn Fein to review its decisions on two Orange Order parades in Belfast.

The commission said not enough extra information was provided to justify a review of the marches on the Springfield and Crumlin Roads.

Alan McQuillan: "We have very clear information"

There are disputes over a number of parades in Belfast on Friday - the Twelfth of July - which is the biggest day in the Protestant marching season calendar.

The parades along the Springfield Road in west Belfast and the Crumlin Road in north Belfast have led to serious disturbances in the past.

The commission also issued a number of other determinations on other marches and called for respect and tolerance to be shown over the next two days.

The police chief's warning follows appeals for calm from Northern Ireland politicians ahead of Friday's marches.

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

"I don't believe people have any excuse for trying to ratchet things up," he said.

Culture Minister Michael McGimpsey hit out at anti-Agreement unionists, accusing them of hijacking and destroying any sense of pride in loyalist culture.