Police in Northern Ireland have appealed for calm after republicans defied calls to cancel a parade in honour of IRA members killed in the troubles.

Sectarian clashes in central Belfast left 56 police officers injured after loyalists attempted to block a republican march on Friday.

Northern Ireland Secretary Theresa Villiers urged organisers to call off the Tyrone Volunteers Day Parade in Castlederg, County Tyrone, saying the event would cause "great hurt" to victims of terrorism and their families.

Organisers refused. Sinn Féin's Martin McGuinness said people should "respect the right" of republicans in Tyrone to observe "an act of remembrance".

McGuinness, who cannot be at Castlederg as he is on holiday, said earlier in the week: "I don't have any other reason to believe that Sunday will not be peaceful - it's not a celebration, it's an act of remembrance."

Sinn Fein's Barry McElduff, an organiser of the Castlederg parade, said he is "absolutely determined" the event will be "peaceful and dignified".

But the Derg Valley Victims Voice said the parade would glorify terrorism and traumatise families affected by IRA violence.

Sunday's event commemorates Tyrone's republican dead, including two IRA members killed as they attempted to build a bomb in 1973.

The march, which is backed by Sinn Féin, has been re-routed away from Castlederg's war memorial after restrictions were imposed by the province's Parades Commission.

Five officers were hospitalised in Friday's violence after police came under sustained attack from bricks and bottles by protesters "intent on creating disorder".

Two members of the public were also injured when rioting broke out as loyalists attempted to block a republican parade that was due to pass along the Royal Avenue shopping districts.

Eight people were arrested.

Vehicles were torched and shop windows smashed as police fired baton rounds to restore order.