London attack – as it happened: Theresa May raises threat level to critical as Isis claims responsibility

Soldiers to support police after 29 people are hurt in tube bombing at Parsons Green

Parsons Green attack: What we know so far

The UK's terrorist threat level has been raised to critical after London was hit by a new terror attack as commuters headed to work on the Tube.

An explosion at Parsons Green underground station in the west of the capital injured passengers and led to a "major incident" being declared. Yet more people were hurt during the crush to leave the train, witnesses said.

Images shared online appeared to showed a bucket with wires trailing from it smouldering inside a District Line train.

The device is being forensically examined while detectives are scouring CCTV and examining witness statements for potential leads.

Armed police, paramedics and firefighters were all called to the scene.

Witnesses described flames and a "fireball" following the incident at about 8.20am today.

Assistant Commander Mark Rowley, who is the UK's top counter-terrorism officer, said the force continues to "chase down suspects" in connection with the attack.

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Key Points

• Explosion at London Tube station leaves 29 injured
• UK terror threat level increased to 'critical', the highest level
• Met deploys extra 1,000 armed officers to hunt terror suspects on the run
• Isis claim responsibility for attack
• 'That could have been me': Parsons Green residents try to process local bomb attack
• Police dismiss Donald Trump terror suspect claim, saying 'we don't even know who the suspects are'

[15 September 2017 12:00 · Jon Sharman]

[15 September 2017 12:00 · Jon Sharman]

Mr Trump is still tweeting. He said: "We have made more progress in the last nine months against ISIS than the Obama Administration has made in 8 years.Must be proactive & nasty!"

[15 September 2017 12:05 · Jon Sharman]

In his update, the Met's assistant commissioner Mark Rowley said most of the 18 injured had suffered "flash burns" from the explosion. His investigators had "many urgent enquiries ongoing" and were working with MI5 intelligence experts, he added.

[15 September 2017 12:14 · Jon Sharman]

NHS England has said 22 people are being treated in four hospitals after the bombing.

[15 September 2017 12:19 · Jon Sharman]

US President Donald Trump has said the internet must be "cut off" to help prevent future terror attacks.

[15 September 2017 12:29 · Jon Sharman]

Donald Trump has called the perpetrator of a bombing on the London Underground a "loser terrorist" who was "in the sights of Scotland Yard". 

It is unclear whether the statement was the result of information he has been passed by aides.

The Metropolitan Police declined to comment.

[15 September 2017 12:32 · Jon Sharman]

Theresa May's former chief advisor, Nick Timothy, has responded to Mr Trump's claim the terrorist was "in the sights" of police.

He said: "True or not - and I'm sure he doesn't know - this is so unhelpful from leader of our ally and intelligence partner."

Mr Timothy and his colleague Fiona Hill were sacked after the Conservatives lost their Commons majority in the June general election.

The UK complained to the Americans earlier this year when sensitive intelligence and on-scene imagery from the Manchester Arena bombing was published in US media before British police had released it.

Home Secretary Amber Rudd said she had been assured a similar breach of confidence would not happen again.

[15 September 2017 12:39 · Jon Sharman]

London mayor Sadiq Khan has said a "manhunt is underway" following the explosion.

"The person or people responsible for this attack will be caught," he said.

[15 September 2017 12:43 · Jon Sharman]

Improvised device 'attached to a timer' was used in London tube explosion

[15 September 2017 12:50 · Jon Sharman]

The Met's former head of counter-terrorism has called the scale of terror in the UK in 2017 "unprecedented".

Richard Walton said: "5th UK terror attack in 2017 - 6 other terror plots stopped - 379 arrests -105 charged - 32 convicted- unprecedented."