Armed Soldiers Outside Horse Guards Parade

Armed soldiers are being stationed outside the entrance to Horse Guards Parade in Whitehall amid increased fears of terrorist attacks on ceremonial troops in the wake of the Canada shootings.

Soldiers armed with rifles have been seen at the central London location where hundreds of tourists gather every day to watch the Changing of the Guard.

Sources told Sky News the move is designed as an overt show of security outside what is an operational military barracks.

The entrance to Horse Guards Parade is part of the Buckingham Palace estate and is usually watched over by two guards on horseback from the Household Cavalry Regiment, alongside two on foot.

But since the start of the week troops in combat fatigues have been visible to visitors.

In a statement the Ministry of Defence said: "The MoD routinely reviews the security arrangements of all of its establishments. Clearly we do not comment publicly on the substance of these."

Sky News understands local commanders will have taken the decision to deploy armed troops outside Horse Guards Parade, which will be the base for former Apache helicopter pilot Prince Harry who has taken a desk job with the army.

Members from the Household Cavalry permanently guard the entrance on Whitehall, which runs between the Houses of Parliament and Trafalgar Square.

Downing Street and Government departments line the route meaning security is always intense, but the sight of armed troops will come as a surprise to many and is intended as a powerful security statement.

The move comes as MPs are being given advice on what to do in the event of an attack in Parliament and are being told to be extra vigilant.

The US has also announced it will boost security at government buildings after threats from Islamist groups.

Last week, Corporal Nathan Cirillo , 24, was shot in the back as he stood on guard at the war memorial in Ottawa.

The gunman, Michael Zehaf-Bibeau, went on to storm Canada's parliament complex before he was shot dead.