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.

Please allow a moment for the liveblog to load.

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 22:48 · Adam Withnall]

London Mayor Sadiq Khan has issued a statement condemning the "evil and cowardly" terror attack and warned people to remain vigilant over the coming days.

[15 September 2017 23:06 · Adam Withnall]

Finally, our front page: 

[15 September 2017 23:29 · Adam Withnall]

A little more information on Operation Temperer: 

- The plan, which was first revealed in 2015, means more than 3,000 extra troops are deployed to help the police cope with the increased demands on their time during the first critical few days of counter-terrorism. 

- The first time it was ever put into place was in May this year when Theresa May activated following the Manchester Arena bombing where 22 people were killed.

- According to the Ministry of Defence, Ms May has only activated the first phase of Operation Temperer so troops will only be deployed to protect nuclear sites and other key security targets. 

- This is not because the Government or the security services necessarily believe that they are under threat but because it frees up the specialist police officers at those sites to work on the counter-terrorism operation.

- It is linked to the decision by the Joint Terrorism Analysis Centre (JTAC) to raise the threat level from severe to critical - meaning a terror attack is expected imminently. 

- Operation Temperer does not normally last more than a few days.

[16 September 2017 01:30 · Kristin Hugo]

That's it for the live blog tonight. Check back tomorrow for the latest updates.