ACC Jackson says officers believe an improvised explosive device was manufactured for the blast.

"Our assumption so far is that this was built by the passenger in the taxi," he said.

"The reason why he then took it to the Women's Hospital is unknown, as is the reason for its sudden explosion."

Investigators are aware of the proximity of Sunday's explosion to nearby Remembrance Sunday memorials, ACC Jackson adds.

"We cannot at this time draw any connection with this but it is a line of inquiry we are pursuing."

ACC Jackson says "significant items" have been found during searches of two addresses in Liverpool.

He says further searches will be necessary today and potentially into the coming days.

An explosion outside Liverpool Women’s Hospital on Sunday has been declared a terrorist incident, police said.

Speaking at a news conference, Counter Terrorism North West’s Russ Jackson said the exact motivation for the blast – which killed one man and injured another – was unclear.

ACC Jackson says that the investigation is continuing at pace. He confirms that - shortly before 11:00 GMT on Sunday - a taxi driver picked up a fare in the Rutland Avenue area of Liverpool.

The fare, a man, asked to be taken to Liverpool Women's Hospital. Upon arrival an explosion occured, he adds.

The cab driver escaped from the car and while he was treated in hospital he has now been released, ACC Jackson says.

Merseyside Police Chief Constable Serena Kennedy and the head of Counter Terrorism North West Russ Jackson have begun the news conference.

Patients have been told to attend appointments as normal following Sunday's explosion.

Security has been tightened however, with a police cordon still in place and officers stopping vehicles for checks as they enter the car park.

Visiting arrangements have been restricted until further notice, the hospital said.

Families of babies on the neonatal unit are asked to contact the hospital.

Everybody is requested to use the new neonatal unit entrance until further notice.

Patients will be notified if their appointments have to be altered.

Image source, Richard Cooke/Geograph

In the next few minutes, we are expecting to hear more from Merseyside Police about the investigation into Sunday's explosion.

We'll bring you the latest updates as they happen here - you can also watch live on the BBC News Channel by clicking the play button at the top of this page.

Three men - aged 29, 26 and 21 - were arrested under the Terrorism Act after being detained in the Kensington area of the city.

Officers from Counter Terrorism North West are leading the investigation, supported by Merseyside Police and security service, MI5.

People detained under the Terrorism Act can be held without charge for up to 14 days.

Image source, PA Media

Boris Johnson has said it appears the taxi driver caught up in the Liverpool explosion acted with "incredible presence of mind and bravery".

Speaking in the past few minutes, the prime minister praised the efforts of the driver involved, who has been named locally as David Perry.

Mr Johnson said: "This is an ongoing investigation so I can't comment on the details or exactly what type of incident it was, what type of crime it may have been.

"But it does look as though the taxi driver in question did behave with incredible presence of mind and bravery.

"But I've got to say this is something that is an ongoing investigation. I think it would be premature to say much more than that."

No increase in terror threat level overnightpublished at 10:50 Greenwich Mean Time 15 November 2021

10:50 GMT 15 November 2021

Frank Gardner
BBC Security Correspondent

There are a number of different lines of inquiry and investigators are keeping an open mind about the cause, and any motivation, after Sunday’s blast.

Unfortunately, the fire that consumed the taxi will have destroyed a lot of the forensic evidence.

Newspapers are speculating that it might have been the detonator that went off and not the main explosive, but there’s been no confirmation of that.

Nonetheless, clearly this does not look like an accident.

It looks like an act of terrorism or a failed act of terrorism - but it has not been declared as such.

The fact this took place just before 11:00 on Remembrance Sunday, not too far from Liverpool Cathedral - where a couple of thousand people were expected to take part in a memorial service - will be one of the factors investigators are looking at.

It is also significant that the national terrorism threat level has not changed. It is currently substantial.

If it was thought there were other people out there with an active and serviceable device, then Britain would have moved up the scale, possibly even to critical - the highest alert level.

Two properties in Liverpool were raided by armed officers about two hours after the blast.

Three arrests took place in Sutcliffe Street, in Kensington, where witnesses reported seeing police approach a terraced house.

The first raid happened at about 13:00 on Rutland Avenue - roughly 0.75 miles from the hospital.

The second operation took place an hour later at about 14:00 around Sutcliffe Street and the adjacent Boaler Street, about a mile from the hospital -

Image source, PA Media

Welcome to our live coverage of developments at Liverpool Women's Hospital.

Here’s what we know so far:

• Three men have been arrested under the Terrorism Act after after a man was killed in a car explosion outside the hospital on Sunday.
• The taxi, which was carrying one passenger, pulled up just before 11:00 GMT, as a national two minutes' silence was due to begin for Remembrance Sunday.
• The passenger was declared dead at the scene and is yet to be formally identified.
• The taxi driver, named locally as David Perry, was taken to hospital and was said to be in a stable condition.
• Mr Perry’s actions have been praised by the city’s mayor Joanne Anderson. She said he had made "heroic efforts" to avert what could have been an "awful disaster" on Remembrance Sunday.

Image source, Carl Bessant