A major investigation is ongoing in Southport after a stabbing attack at dance class earlier today.

Over the last few hours, forensic officers and emergency services have been pictured close to where the incident happened:

Image source, PA Media

Image source, EPA

Image source, EPA

King Charles III says he and Queen Camilla are "profoundly shocked to hear of the utterly horrific incident" in Southport.

"We send our most heartfelt condolences, prayers and deepest sympathies to the families and loved ones of those who have so tragically lost their lives, and to all those affected by this truly appalling attack," he says in a statement.

Emily Spurrell, Merseyside's Police and Crime Commissioner, says she is "utterly shocked and devastated" by the incident in Southport.

"I cannot even imagine the untold pain and heartache they are facing. My thoughts are also with all those who suffered injuries and who have been affected by this harrowing incident," she says in a statement.

The attack on "innocent, defenceless children" at a dance school Taylor Swift-themed event during their summer holidays is "unthinkable and absolutely abhorrent", Spurrell adds.

"These young people had their whole lives ahead of them and it is hard to find the words to convey our deep sadness.

"Our region will be heartbroken that more young lives have been lost at the hands of violence and more have suffered serious injuries, and I share local people's deep concern and anguish," she says.

Image source, Reuters

Warning – this post contains distressing details.

• The attacker, described as wearing a face mask, arrived on Hart Street in a taxi and refused to pay the fare, one witness said
• Multiple people reported seeing several young children bleeding in the road after being stabbed
• Several witnesses also say they heard a woman running down the road screaming "my daughter's been stabbed"
• Another witness said they took around 10 girls to safety in a nearby house
• A local therapy nurse, who spoke to a mother of one of the victims, says her own daughter heard a "sinister scream" around the time of the attack
• A local journalist said he "never seen anything like it", as he described seeing a young girl being carried on a stretcher

We're now hearing from Prime Minister Keir Starmer.

He says the events today are "truly awful" and the "whole country is deeply shocked".

Starmer says it's "almost impossible" to imagine the grief those affected by the attack are going through.

He praises the emergency responders, thanking them for the "professionalism" they showed.

Here's what we learned from Merseyside Police Chief Constable Serena Kennedy's update:

• Two children were killed in what she called a "ferocious attack"
• Nine children other were injured, six of whom are in critical condition
• Two adults are also in critical condition, who police believe were "bravely trying to protect the children who were being attacked"
• The children are understood to have been attending a Taylor Swift-themed event at a dance school
• The person arrested on suspicion of murder is a 17-year-old male from nearby Banks, originally from Cardiff
• The attack is not being treated as terror-related

We're now hearing from North West Ambulance Service's Dave Kitchin.

He says the ambulance services were called after reports of multiple stabbings.

Paramedics treated 11 casualties, he says, and he thanks staff who worked hard to care for the victims.

The incident will have a lasting impact on the whole community, he says.

Kennedy says the investigation is still in its early stages and the motivation is still unclear.

At this time the investigation is not being treated as terror-related, she says.

Remember - you can watch the news conference by pressing Watch live above.

Kennedy goes on to say it's understood the children were attending a Taylor Swift-themed event when the attacker entered.

The police believe the two adults injured were intervening in the attack, she says.

Kennedy says the 17-year-old – who, she says, was arrested on suspicion of murder over the "ferocious attack" – was originally from Cardiff.

He was living in Banks, near Southport, she adds.

We're hearing from the police and emergency services now.

Chief Constable Serena Kennedy says it is with great sadness that two children have died.

She adds that nine others have been injured, and six are in critical condition.

Two adults are also in critical condition, she says.

Merseyside Police say their update on the stabbing has been delayed slightly.

We'll bring you more when we have it.

We're expecting to hear an update from Merseyside Police in Southport soon.

We'll be bringing you updates here on this page, but you can also follow our live stream by pressing the "Watch live" button at the top of this page - or click below.

Emma Pengelly
BBC News

Emma Longman, who works at a nearby supported living accommodation, describes feeling "panicked" after her workplace received a "safeguarding alert" from police following the attack.

She and her colleagues closed windows and blinds and secured the back gate, she says.

"[Initially] we didn’t know what was going on," she says.

"We could hear the police outside, we thought maybe it was a road accident.

"The son of one of our support workers was in a different holiday club, she got a phone call saying to go and pick him up.

"I felt really panicked, we didn't know what was going on. Everyone was a bit on edge and scared.

"When we found out it was a stabbing we thought ‘oh my god, are they still out there?’"

Local nurse Joanne Niemen, 49, spoke to our team in Southport earlier:

We've just had these pictures from Hart Street in Southport, where officers continue to collect evidence.

Image source, PA Media

Image source, PA Media

Here's the full update from Merseyside Police:

"We can confirm that a 17-year-old male from Banks, who was arrested in connection to the stabbing in Southport this morning, Monday 29 July, remains in police custody and will be questioned about the incident.

"At this early stage, enquiries are ongoing to establish the motive for this tragic incident and we would urge people not to speculate while the investigation is ongoing.

"We can also confirm that the incident is not currently being treated as terror-related and we are not looking for anyone else in connection with the incident.

"Any updates will be provided to the public when available.

"Communities can also follow Merseyside Police on social media for updates and if they want to submit information, they can do so on the Merseyside Police website or Crimestoppers."

We've just had an update from Merseyside Police, who say a 17-year-old male from the nearby village of Banks was arrested in connection with the stabbing.

"We can also confirm that the incident is not currently being treated as terror-related and we are not looking for anyone else in connection with the incident," officers say.

Erica Witherington
Reporting from Southport

A woman living near the scene of the attack has described hearing a scream for help from a mother whose daughter had been stabbed.

The woman, who does not want to be named, tells the BBC the mother said her daughter was "barely conscious".

"I’ve never seen anything like it. We didn’t know what was going on," the woman says.

She says the girl is one of the victims taken to Alder Hey Children's Hospital for treatment.

She says she called 999 repeatedly "because no one was coming to help us" - adding that emergency services told her to stay indoors.

Jenny Coleman
Reporting from Southport

Ken, who lives in Oak Street off Hart Street, says he started hearing about the incident when neighbours told each other to "go in and lock your doors".

"It's normally a quiet area," he says. "There are business premises at the back of these houses."

He adds: "I usually see young mothers going from their cars up the passageway. I just wonder what the world is coming to."