Thirteen civil rights protesters were shot dead by British soldiers on January 30 1972 in the city.

Another man died four days later, and while many consider him the 14th victim his death was attributed to an inoperable brain tumour.

Only one suspect - identified as "Soldier F" - was ever charged. He was facing prosecution for double murder, but the case collapsed last year before it had begun.

Family members gathered at Creggan Shops in Londonderry before walking to the Bloody Sunday monument in Rossville Street for the annual memorial service and wreath-laying ceremony.

Religious and community leaders gave readings and the names of those who died were read aloud, as one man vowed to fight on for justice, adding: "We have travelled a long road from the horror of that day."

At 2.30pm, a 50th-anniversary march will take place from the Creggan Shops to the Free Derry Wall.

Speakers will address the rally including Kate Nash, the sister of William Nash who was killed, and daughter of Alexander Nash who was wounded going to his aid.

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Later today, the President of Ireland Michael D Higgins will deliver a recorded message to the Bloody Sunday families.

It will be shown publicly during a commemorative event, Beyond the Silence, due to take place before a limited audience. His message will also be live-streamed online.

The event will be hosted by actor Adrian Dunbar and will feature tributes to the victims, as well as music and public performances.

The theatre will fall silent at the precise time when, 50 years ago, paratroopers opened fire.

Tanaiste Leo Varadkar said: "Today we remember the 14 innocent people who were killed in Derry 50 years ago on Bloody Sunday.

"The events of that day cast a long shadow over the city and the country that many are still dealing with today.

"We salute the courage and perseverance of the victims and their families who have campaigned tirelessly for justice and who continue to do so today.

"Their tenacity serves as an example to other Troubles-related victims to never give up the fight for justice.

"We pledge to honour the memory of those who died on Bloody Sunday by standing with all victims of the Troubles and continuing to work for permanent peace on our shared island."