Amid the pomp and ceremony of Changing the Guard, they stand out from the hundreds of tourists.

Armed to the teeth with firepower, the beefed-up police firearms officers are helping protect our soldiers from terror attack.

Police carrying powerful Heckler and Koch G36C semi-automatic rifles and Glock 17 9mm pistols patrolled on Horse Guards Parade in Whitehall, central London, earlier today.

The armed police officer, who was seen patrolling Horse Guards Parade earlier today carrying several powerful weapons

Security has been bolstered tourist hotspots following the shooting of a ceremonial guard outside the Canadian parliament.

Each morning delighted visitors from around the world watch Changing the Guard, where troops in traditional red tunics on horseback perform historic ceremonial duties.

The buildings at Horse Guards are the headquarters of the Army's London District and provide accommodation for soldiers in the Queen's Life Guard, a unit which carries out its duties and performs on state occasions.

Last week, senior Army officers made the decision to deploy armed troops there after Corporal Nathan Cirillo, 24, was shot dead by an Islamist fanatic two weeks ago while on unarmed guard duty at the National War Memorial in Ottawa.

The heavily armed police officers who were spotted for the first time today patrolling Horse Guards Parade in central London during the daily Changing of the Guard ceremony

His killer, Muslim convert Michael Zehaf-Bibeau, was shot dead by the Sergeant-At-Arms when he stormed the parliament, firing a shot into the door of the room where Canadian Prime Minister Stephen Harper was hiding a cupboard.

There are fears a ‘lone wolf’ extremist radicalised by Islamic State could attempt to murder a British soldier.

Last year, Drummer Lee Rigby was butchered in cold-blood by Muslim fanatics outside his barracks in Woolwich, south-east London.

The officers were seen carrying Heckler and Koch G36C semi-automatic rifles and Glock 17 9mm pistols

Armed Metropolitan Police officers are patrolling the city’s landmarks to protect tourists, soldiers and citizens, while deterring potential militants from launching a strike.

A Metropolitan Police spokesman declined to comment on whether police security arrangements had been stepped up in the wake of the Canadian attack.

But he said: ‘Armed officers routinely patrol central London and iconic locations. It is not a big surprise.’

Last week it emerged Westminster was on high alert in case of a terrorist attack on Parliament.

MPs have been told to consider fitting their constituency offices with panic buttons and designating a 'safe room' in their homes.

Security has been beefed up after an unarmed soldier in Canada was shot dead at the country's national war memorial. Westminster has also been placed on high alert in case of a terrorist attack on parliament

The armed officers stood out among the tourists who were in Horse Guards Parade earlier today to see the Changing of the Guard

He said: ‘An enhanced number of officers for high visibility policing have been deployed across the country and this will continue for the foreseeable future.

'In addition to this there will be an increase in vehicle checkpoint searches, extra patrols and other security measures including providing security advice to businesses and partners.

'Any additional measures that are needed will be taken.