Relatives of 13 civil rights protesters shot dead in Northern Ireland by British soldiers 50 years ago demanded justice on Sunday, as they commemorated one of the darkest days in modern UK history.

The "Bloody Sunday" victims' names were read out under a leaden sky to the mournful notes of an Irish flute, as the relatives and hundreds of supporters gathered for a memorial event in the city of Londonderry -- known as Derry to pro-Irish nationalists.