Events are being held across Scotland to mark the 100th anniversary of the Battle of the Somme.

The conflict, which was fought between July and November 1916, cost hundreds of thousands of lives.

British and Commonwealth troops suffered nearly 20,000 casualties in the first day of fighting alone.

At 7.28am on Friday, the One O'Clock Gun was fired at Edinburgh Castle to mark the moment the battle began, when mines were blown up beneath the German lines.

It was followed by a two minute silence which ended with the blowing of a whistle used to send British troops over the top a century ago.

The Battle of the Somme was intended to achieve a decisive victory for the British and French against Germany's forces in the First World War.

But after 18 weeks of bloody fighting, Allied troops had advanced less than ten miles into German-held territory.

When the battle ended on November 18, British and Commonwealth troops had suffered 420,000 casualties. French losses numbered around 205,000 and the German army suffered 465,000 casualties.

The First Minister will attend a ceremony in France on Friday.

Actors dressed as soldiers were spotted walking through Glasgow city centre, as tribute to those who fell.

When approached the said nothing and handed over cards showing the names of the real soldiers who died at the battle in July 1916 as part of a performance piece to those involved.

In Fife, a sand drawing "Somme Soldiers" by Sand In Their Eye, was created on the beach in Elie to commemorate the anniversary, as part of the East Neuk Festival.

Nicola Sturgeon said: "It is now exactly 100 years since the start of the Battle of the Somme - the opening day of which has gone down in history as one of the bloodiest in the history of armed conflict.

"Fifty-one Scottish battalions were involved, and the losses suffered by those units - and those from the other countries involved - were on an almost unimaginable scale.

"Barely a single community in Scotland was left untouched by the battle. Across Scotland communities are now remembering those who gave their lives, and a whole century on from the devastation and suffering of the Battle of the Somme, we should all reflect on the horrors of the Great War and give thanks that our continent now lives in peace."

In Glasgow, paving stones remembering two local soldiers who won Victoria Crosses in the battle will be unveiled.

Wreaths will be laid at the People's Palace in Glasgow Green to remember sergeant James Turnball at 12.30pm and, an hour later, drummer James Ritchie.

An overnight vigil in Banchory, Aberdeenshire, was followed by wreath-laying at the Burgh and Gordon Highlander Memorials.

In Dundee, the Law war memorial will be lit to mark the Somme commemorations from 6am until midnight.

Memorials and ceremonies are also being held across the rest of the UK and in France.

The Queen and senior royals will lead the nation in commemorating the battle by attending services in both countries.

The Duke and Duchess of Cambridge and Prince Harry will attend a vigil in memory of the fallen in France.

Major general Mark Strudwick, chairman of the Trustees of the Scottish National War Memorial, added: "The courage and sacrifice of the British soldiers who fought at the Battle of the Somme should never be forgotten.

"Few words conjure the tragic scale and staggering loss of life during the 141 days that battle raged.

"One hundred years on we come together to honour them, to remember them and to ensure their memory and legacy lives on for generations to come."