Britain is on critical terror alert with soldiers and increased numbers of armed police officers being deployed amid fears of another atrocity being committed imminently.

Prime Minister Theresa May has raised the threat level to the highest possible rating, and suggested Manchester attacker Salman Abedi did not act alone.

She said a "wider group of individuals" could have been involved in the blast at a concert by US pop star Ariana Grande at the Manchester Arena that left 22 dead and dozens injured.

The military could be deployed to support armed police officers to combat the increased threat, Mrs May added during a live televised statement from Downing Street.

From yesterday: Children among dead as death toll rises after terror attack bombing at Ariana Grande Manchester Arena concert

She will will chair a meeting of the Government's emergency Cobra committee at 9.30am today (Wednesday, May 24).

The public will see more armed officers, working alongside their neighbourhood and specialist colleagues on proactive operations and targeted patrols, both on foot and in vehicles, a Scotland Yard spokesman said.

Commander Jane Connors, leading the London policing operation, added: "We will do all we can to protect the Capital that we serve at this unsettling time.

"We are using every tactical option - not just through the use of armed officers but ongoing work by the Counter Terrorism Command; working with partner agencies and gathering community intelligence.

"Whilst some of what we are doing will be obvious to the public there is a huge amount of work happening day and night that the public will never know about."

From yesterday: Mayor of London Sadiq Khan: There will be more police on the capital's streets

The country's senior anti-terror police officer, meanwhile, said there were "gaps in our knowledge" about Abedi which had led to the increased threat level.

Metropolitan Police Assistant Commissioner Mark Rowley said: "We are moving at pace, we are making arrests, we are doing searches but - not unsurprisingly - there are still gaps in our knowledge.

"Whilst we are chasing those gaps down, on a precautionary basis, based Anyone concerned about suspicious behaviour, or who has information they believe may help police, should call the Anti-Terrorist Hotline 0800 789 321. They do not have to give their name and all information received via the hotline is confidential.on that judgment, JTAC (the Joint Terrorism Analysis Centre) have made this judgment about the threat level and we will respond in our policing stance to that decision."

From yesterday: Metropolitan Police Commissioner Cressida Dick condemns 'appalling' terrorist attack

So-called Islamic State claimed responsibility for the barbaric attack, which involved a home-made device packed with nuts and bolts which exploded in the venue's foyer as thousands of young people were leaving.

Abedi, a 22-year-old Salford University drop-out, is believed to have been born in Manchester and of Libyan descent, has been named as the suicide bomber.

He is thought to have attended the Manchester Islamic Centre, also known as Didsbury Mosque, along with his parents and siblings.

Anyone concerned about suspicious behaviour, or who has information they believe may help police, should call the Anti-Terrorist Hotline 0800 789 321. They do not have to give their name and all information received via the hotline is confidential.