A wartime bomb at the centre of a three-day defusing operation has exploded in what police said was an accidental detonation.
The blast was heard across Great Yarmouth in Norfolk at 5pm, shortly after officers said they had changed their approach to safely detonating the bomb.
They confirmed that it was not a planned detonation, and that all emergency services had been accounted for.
Footage shot by ITV News Anglia shows a huge explosion with flames and smoke rising, and pieces of debris blown high into the air.
People living in the town reported their windows being shaken by the blast, though emergency services said no injuries have been reported.
ITV News Anglia reporter Rob Setchell reported from the scene of the explosion on Friday (Image: Norfolk Police/Twitter)
Norfolk Constabulary's Assistant Chief Constable Nick Davison said mitigation measures had been put in place to guard against the impact of an unintended detonation.
“The device detonated shortly after work had started to disarm the device," he said. "The approach had been the safest option to disarm the device, however, it always carried a risk of unintended detonation.
“Thankfully, all personnel have been accounted for and agencies are coming together to assess damage to the river wall.”
The team in charge had abandoned attempts to cut through the bomb's outer casing earlier on Friday afternoon, as water from the operation was destabilising the sand barrier built around the 250kg device.
Bomb disposal teams then started on what they said was the "one option" left to them - of slowly burning off the explosive in the hope of making the bomb safe.
But they warned that the operation carried a risk of an "extremely large blast", and warned people to stay outside the 200m cordon.
The bomb was found at Bollard Quay on Tuesday lunchtime during dredging by contractors working on the third river crossing in the town.
It was found to be a metre-long Second World War device, which was assessed to be unstable and unable to be moved.
A huge sand barrier was built around the bomb to minimise any damage from a blast, before work began on separating the trigger and fuse from the explosive charge.
Jack Onyett, who lives opposite the quay where the bomb went off, said it was a "very scary" experience.
“When it went off I was a bit worried because my house is so close. I was more worried about my house going up.
"Now it’s all over hopefully we can get back in the next few hours.
"It was very scary. Not many people have seen a World War Two bomb blow up and it was very scary.”
Great Yarmouth bomb: Timeline of an explosion
11.30am Tuesday - The bomb is found during dredging works and a 400-metre perimeter is set up around the bomb.
Tuesday evening - Homes are evacuated and emergency rest centres are set up for residents to stay overnight.
11pm Tuesday - A major incident is declared by authorities.
Noon Wednesday - Bomb disposal experts build a sand tower around the device to create a blast barrier.
Wednesday afternoon - Police warn that people must leave their homes as shrapnel injuries are a risk and explosion is a ‘real possibility’.
Thursday morning - People are urged to stay away as the bomb is due to be detonated after two days of preparations. Army experts subsequently discover gas pipes forcing them to delay their plans to safely detonate the "unstable" device.
Thursday evening - A remote-controlled robot begins cutting through the outer casing of the 250kg device despite fears of the gas mains.
Friday morning - Work to defuse the bomb continues and enters the final stages.
1.30pm Friday - Work halted after water used to cut into the bomb destabilised the sand defences built around the device.
4.30pm Friday - Army bomb disposal experts abandon attempts to cut into the device and change their tactics, using a technique that creates a slow burn of the explosives. Public warned of extremely large blast.
5pm Friday - Huge blast is felt across Great Yarmouth as police say the bomb exploded in an "unplanned detonation".
7.45pm Friday - Residents are told they can return to their homes, with the 200m and 400m cordons lifted.
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