The centenary of the first official memorial to be erected on the Western Front to remember the First World War dead has been marked.

The Ulster Tower stands close to the scene of the Battle of the Somme in Thiepval in northern France.

The battle saw an estimated 5,000 casualties from the 36th Ulster Division on the first day alone - of whom 2,000 died.

Northern Ireland First Minister Paul Givan, DUP leader Jeffrey Donaldson and European Affairs Minister Thomas Byrne were among guests who attended a special service to mark the centenary.

Presbyterian Moderator Dr David Bruce, Methodist President Dr Sahr Yamhasu and Church of Ireland Primate John McDowell took part in the service.

The Bugles, Pipes and Drums of The Royal Irish Regiment, along with the regimental band, and the band of 2 Brigade in the Irish Defence Forces also took part.

Mr Givan said the sacrifice made by both of the two major traditions in Ireland in the First World War should always be remembered.

"It's an honour for me to be here today on this historic occasion to mark 100 years of the Ulster Tower which memorialises the sacrifice that was made by the men of the 36th Ulster Division and remembers those who served from right across Ireland in the First World War," Mr Givan said.

Mr Byrne represented the Irish Government at the event and laid a wreath to remember all those from Ireland who died in the First World War.

He also visited the nearby town of Guillemont,where he laid a wreath at the Celtic Cross First World War monument which stands in remembrance of the 16th Irish Division.

"This event is about a shared commemoration of all those from the island of Ireland who lost their lives in the First World War," he said.

"It is about remembering the enormous and destructive impact of the war on that generation, and how it has shaped our history.

"We have come a long way indeed in ensuring that this chapter of our history is fully recognised and better understood as part of our shared heritage."