Twelfth of July parades in Belfast have passed off peacefully, according to UTV reporter Marc Mallett.
Three men were stabbed in the early hours of Saturday morning in sectarian clashes ahead of the parades.
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The memorial service will be attended by Prince Harry and Meghan Markle.
David Browning admits manslaughter by diminished responsibility but denies murder.
Four people have died and the suspect is still at large, police said.