24/05/2017 9:41 PM AEST | Updated 25/05/2017 12:58 AM AEST

'Critical' UK Threat Level See Armed Soldiers Hit Britain's Streets

Armed soldiers began their patrols of UK streets and high-profile targets on Wednesday in the wake of the deadly Manchester Arena bombing.

Monday’s atrocity claimed 22 lives and injured 119 others, in the worst terror attack to strike Britain since the 7/7 London blasts in 2005. 

Military personnel were photographed surrounding Parliament at Westminster, which will be closed to the public “until further notice”. Troops were also spotted outside Number 10 Downing Street.

[LIVE BLOG: UK Terror Threat Level Raised To ‘Critical’]

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Armed soldiers were pictured arriving at Parliament on Wednesday amid a "critical" terror threat level
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The unusual sight of military service people arriving at Parliament comes amid increased security
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Troops were spotted outside Number 10 Downing Street on Wednesday
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Police working alongside troops at Downing Street on Wednesday 
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British soldiers enter a Ministry of Defence building near to New Scotland Yard police headquarters near to the Houses of Parliament
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Soldiers will work alongside armed police to secure key sites across the UK
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Soldiers arrive near Buckingham Palace on Wednesday
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Soldiers will work with police to secure key UK sites
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Soldiers arrived to help police secure key sites across London on Wednesday
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Military personnel will complement armed police officers under increased security measures introduced on Tuesday

The UK terror threat level has been raised to ‘critical’, meaning more attacks may be imminent.

It comes after Home Secretary Amber Rudd suggested suspected Manchester bomber Salman Abedi was part of a network of terrorists. Abedi’s 23-year-old brother was arrested on Tuesday. Three more arrests took place today.

Soldiers will work under the supervision of the police and will bolster armed officers across the capital, and in other major cities, towns and transport hubs as part of a wave of increased security measures put in force last night.

[LIVE BLOG: UK Terror Threat Level Raised To ‘Critical’]

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Tourists stand aside as two armed officers stride through Westminster on Wednesday
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Armed police patrol a street near the Palace of Westminster housing the Houses of Parliament on Wednesday

Just after midday on Wednesday, around 20 troops arrived at the ‘Peers’ Entrance’ to Parliament.

A mix of Paratroopers and Guardsmen, the fully armed soldiers then fanned out through the Palace of Westminster.

Some went to man the ‘Black Rod’s Entrance’, where visitors arrive at the House of Lords. Others were sent to Portcullis House, the next modern extension of the House of Commons.

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An increased presence of armed police will be noticed by commuters across the country
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Increased security measures were in place by Tuesday evening across the UK, including in Manchester 

Some soldiers were put on sentry duty, checking passes of those arriving at Parliament. 

It was an odd experience for those used to working at Westminster.

The Ministry of Defence said the Changing the Guard ceremony at Buckingham Palace was cancelled to redeploy police officers.

The decision came before a man with a knife was arrested close to the Palace on Wednesday, though this was not believed to be terror related.

Scotland Yard confirmed this morning that Buckingham Palace, Downing Street, the Palace of Westminster and embassies will all be protected by the military, freeing up the police for other duties.

Concerts and sports events may see similar protection in coming weeks.

This morning, Home Secretary Amber Rudd has said she “absolutely” expects the raising of the threat level to critical to be temporary. But she confirmed that the hunt was on for others. “

It was more sophisticated than some of the attacks we’ve seen before, and it seems likely - possible - that he wasn’t doing this on his own,” she told the BBC.

Rudd also told Sky this intriguing line on bomber Salman Abedi: ”We do know he was known up to a point to the intelligence services”.

And she added she was “irritated” by leaks in the US about his identity and the nature of the attack.

She may be even more irritated that the French are now leaking further intel.

[LIVE BLOG: UK Terror Threat Level Raised To ‘Critical’]