LONDON (AFP) - Queen Elizabeth II lead Britain in paying silent tribute to the Commonwealth war dead on Remembrance Sunday, an annual event made particularly poignant this year on the centenary of the start of World War I.
The 88-year-old monarch, senior royals and politicians including Prime Minister David Cameron laid wreaths at the Cenotaph national war memorial in London, as hundreds of veterans from more than 70 years of conflicts looked on.
Security was tighter than normal amid heightened fears of the risk of a terror attack, but there was no change to the customary programme of marches and military music.
A 13-pounder World War I gun was fired at 1100 GMT (7pm Singapore time), marking the start of two minute's silence observed by millions of people across Britain and at British military bases across the world.
Remembrance Sunday is the Sunday closest to Armistice Day on November 11, the anniversary of the 1918 signing of the peace that ended fighting in World War I.
More than one million people from the British empire died in the four-year conflict, but the day has become a time to remember all the troops killed in wars since then.
It is thought there has been only one year - 1968 - without a British military fatality on active service since the end of World War II in 1945.
Cameron said the ceremonies were "particularly poignant" as 2014 is the centenary of the start of World War I, as well as the 70th anniversary of the D-Day landings and the end of Britain's combat role in Afghanistan.
"Today we stand united to remember the courageous men and women who have served our country, defended our freedoms and kept us safe," he said ahead of the event.
"We remember all those who have fallen and those who have risked their lives to protect us."
Security this year was "intensified" following fears the event could be a target for attack, according to the head of Britain's armed forces, Chief of Defence Staff General Nicholas Houghton.
Police arrested four men overnight Thursday on suspicion of "Islamist-related terrorism", which media reports said concerned a plot intended for British soil.
"Certainly the proximity of the sense of threat for this weekend, which has intensified the nature of the security that's attendant on it, has contributed to quite a different feel about this year," Houghton told BBC television.
The national terror level was also raised in August to "severe", meaning an attack is "highly likely", due to fears over the threat of the Islamic State in Iraq and Syria.
Scotland Yard said it had an "appropriate and proportionate" policing plan in place for the London commemorations.
The queen laid the first wreath followed by her husband Prince Philip, 93, her son and heir Prince Charles and grandson Prince William, all of whom have served in the military.
Forty-six high commissioners from Commonwealth countries then each laid a wreath.
And in a sign of the improved relations between Ireland and Britain, the Irish ambassador laid a wreath for the first time in honour of thousands of Irishmen who died in British uniform.
Meanwhile Cameron has launched plans for a £1-million (S$2.05-million) national memorial to the more than 220,000 troops who fought in Iraq and Afghanistan since 2001, 632 of whom died.
Cameron wants the memorial to be opened in 2016, a decade after British troops first entered Afghanistan's troubled southern Helmand province.
In the run-up to Remembrance Sunday, many Britons wear a paper red poppy symbolising the flowers which grew on French and Belgian battlefields during World War I.
This year, the moat of the Tower of London has been filled with 888,246 ceramic poppies in a striking art exhibit to mark every single British soldier who died during that conflict.
An estimated four million people will see the installation, called "Blood Swept Lands And Seas Of Red", before it is taken down at the end of November.