SECURITY is expected to be stepped up as Celtic arrive in Belfast tomorrow for a vital Champions League qualifier in the wake of rioting in the Northern Irish capital.

Police in Northern Ireland have given assurances that Wednesday'stie against Cliftonville would still go ahead.

Police have described the rioting over the weekend in the Woodvale area of north Belfast as "attempted murder on officers".

Police Scotland say they had not been notified that any of their officers had been hurt in the three days of violence involving Orange Order marchers, in which 44 officers were injured.

A number were hospitalised with suspected broken bones, head or neck injuries after being attacked with Orange Order ceremonial swords, bricks, bottles and heavy masonry. Others were treated for heat exhaustion.

Hundreds more police officers are expected to be deployed to Northern Ireland from forces across the UK if the violence continues.

Initially, some 600 police from mainland Britain, including almost 120 frontline officers from Scotland, were drafted in to help the cash-strapped Police Service of Northern Ireland (PSNI) at the traditional Twelfth of July marches.

But after widespread clashes, another 400 officers from across the UK were called in. More than 1000 British officers are now providing support.

The mutual aid officers from England, Scotland and Wales will continue to be used to bolster numbers at flashpoint areas in north and east Belfast.

Senior police commander Assistant Chief Constable Will Kerr added: "We will probably bring more mutual aid officers to continue through the week and for as long as it is necessary.

"The Chief Constable has made it very clear we will have as many resources on the streets of Belfast for as long as it takes to protect communities and our officers across Northern Ireland."

The policing bill has already run into multiple millions of pounds and comes on top of the £20m bill generated by policing loyalist flags protests earlier this year.

A PSNI spokeswoman said of the Celtic arrangements: "As with any major event police will take all relevant information into consideration beforehand in order to provide an appropriate and proportionate policing operation to ensure the safety of public and the success of the event."

Yesterday the Crumlin Road was closed after a pipe bomb was thrown at police.

The unrest came after a Parades Commission determination that a parade by three Orange Order lodges would not be allowed to march along a stretch of the Crumlin Road that separates loyalist and nationalist communities on its return journey from the main Belfast July 12 demonstration.

ACC Kerr urged loyalists to stay off the streets in Northern Ireland amid heightened tensions over a parades dispute.

He also called for mature political leadership and for the Orange Order to call off protests to prevent further violence, which has already cost the economy "multiple millions of pounds".

He said: "We need a calm few days, we need discouragement from people to come on to the streets and, if we could reduce tensions over the next few days, particularly in light of the Assembly debate at Stormont tomorrow, hopefully we can get back to a sense of normality very soon.

"We do not need people on the streets of east or north Belfast at the moment."

The Stormont Assembly has been recalled and will meet to discuss the fall out from the Parades Commission determination which prevented Protestant Orangemen from walking past the nationalist Ardoyne area on Friday night.

More than 50 petrol bombs were thrown at police lines, with a further 30 recovered by officers over the past three nights. Police fired 49 plastic bullets in an attempt to quell the trouble.

Meanwhile, the Orange Order, which has been widely criticised for calling people onto the streets without a plan, said the PSNI had questions to answer over the use of water canon and plastic baton rounds.