The Prime Minister was repeatedly asked 'how many more children will die?' as he placed flowers at the scene of the Southport knife rampage today.
Sir Keir Starmer placed his own floral tribute among hundreds of others as he visited the seaside town in Merseyside to offer his condolences to the families who have lost loved ones.
The three girls stabbed to death were today named by police as six-year-old Bebe King, seven-year-old Elsie Dot Stancombe and nine-year-old Alice Dasilva Aguiar. A vigil was attended by thousands of mourners in Southport on Tuesday night.
The Labour leader's brief visit, which lasted around two minutes, was interrupted by some members of the public heckling him.
As the Prime Minister walked past, one man declared: 'Here's your photo opportunity.'
Another shouted: 'How many more children? Our kids are dead and you're leaving already?'
Other furious onlookers shouted 'scumbag', 'time for change' and 'go away, you're not wanted'.
Another woman said: 'I've just found out my friend's nine-year-old daughter was killed, the person I've held as a child, and you can't do s***.'
And a different man shouted: 'Get the truth out!'
It comes after Merseyside Police issued a warning after an 'incorrect' name for the alleged Southport attacker was widely circulated online.
A 17-year-old boy, originally from Cardiff but from the Banks area of Merseyside, remains in custody accused of murder and attempted murder.
Inaccurate posts by social media sleuths about the identity of the perpetrator have received millions of views and engagements.
Prime Minister Sir Keir Starmer arrives with a floral tribute to the child victims of a knife attack
A note from Sir Keir Starmer left at the scene of the 'ferocious' knife attack: 'There are no words for such profound loss. The nation's thoughts are with you'
Earlier today, 'happy smiley' Alice Aguiar, nine, was named after she died in hospital in the early hours of Tuesday following the attack
Elsie Dot Stancombe, seven, was also confirmed to have died on Monday as nine other children and two adult women were rushed to hospital
Six-year-old Bebe King was pronounced dead shortly after the attack in Southport on Monday
Downing Street also warned against 'unhelpful' speculation amid concerns that misreporting online could inflame community tensions.
Officers should be given the space to probe the case without people guessing at the possible motive or circumstances, No 10 said.
The 17-year-old suspect is from Wales, Merseyside Police has said, but false claims that he was an asylum seeker who had arrived in the UK by boat have spread online.
The force is now understood to be monitoring a potential far-right rally in the area.
Sir Keir laid a wreath of pink and white flowers in front of dozens of locals, journalists and photographers.
He said the horrific attack 'touches a nerve' with the whole country as he lay his floral tribute at the scene alongside a note telling the victim's families 'the nation's thoughts are with you'.
After visiting Hart Street, Merseyside he went on to meet the emergency service workers who responded to the horrific tragedy praising the 'incredible' paramedics, firefighters and police officers for 'saving lives'.
'I hope you feel proud of the part that you played in the most difficult circumstances, to do what you could for those young lives,' Sir Keir told them.
The PM's visit comes as the young girls who died in the attack were named and pictured.
Bebe, six, was pronounced dead shortly after the attack while Elsie, seven, was also died on Monday. And earlier today, 'happy smiley' Alice Aguiar, nine, was named after she died in hospital in the early hours of Tuesday.
Five other children, aged between six and 11, remain in a critical condition alongside two female adults, including hero teacher Leanne Lucas, who 'bravely tried to protect them'.
A teenager, born in Cardiff, remains in custody accused of murder and attempted murder. Detectives are probing him on the incident.
The Labour leader went on to visit Southport Police station where he shook hands with the dozens of firefighters and police officers involved, telling them children are 'alive today' because of their brave work.
He told them: 'I know you would go and face any situation that was put in front of you, you do it every day.
'But there's no pretending that what you dealt with yesterday was ordinary or just a usual response. It was really, really difficult. I just wanted to say a personal thank you to each of you, that's why I wanted to shake each of your hands, for what you did yesterday.
'I'm incredibly proud of what you did. I'm amazed, but not surprised, that you're in today, carrying on with your duties. I really want you to focus on the fact that there are children today alive because of what you did yesterday.
'That is incredible. It's what you do every day but it's the most difficult of circumstances. I don't want you to think for a minute the rest of the country has not seen that.'
Sir Keir Starmer shakes hands with emergency workers who responded to yesterday's knife attack in Southport
Prime Minister Sir Keir Starmer leaves a floral tribute to the child victims of a knife attack on Hart Street
Sir Keir said he made the visit to the shocked community to pay his respects to the victims and families who are going 'through raw pain and grief that most of us can't imagine - I can't imagine, as a dad myself'.
The PM had a briefing with Merseyside Police's chief constable and emergency services about their ongoing investigation.
He added that he wanted to make the trip to thank emergency workers in person for their bravery.
'It was very, very difficult,' Sir Keir said. 'They were absolutely professional. And it was important for me to come and say simple words - thank you.'
The Prime Minister's visit to the scene is reported to have been marred by hostile shouts from some members of the public, who called for action on knife crime.
The Home Secretary Yvette Cooper also visited the town to lay flowers at the police cordon in Southport this morning.
She was accompanied by Southport MP Patrick Hurley, Police Chief Constable Serena Kennedy, Fire and Rescue Service's Chief Fire Officer Phil Garrigan and police and crime commissioner Emily Spurrell who walked to the cordon together.
A crew from Merseyside Fire and Rescue Service also paid tribute. About a dozen firefighters walked together to the cordon on Hart Street and laid flowers, with a message to say they were 'thinking of everyone involved'.
Home Secretary Yvette Cooper pays tribute to the child victims of the horror knife attack
Brave Leanne Lucas, 35, (pictured) who organised the Taylor Swift-themed workshop, suffered stab injuries after the man entered the venue through the unlocked door, which was left open amid the scorching heat
Floral tributes near the scene in Southport today after three children died and nine were injured
The Home Secretary stood for a few moments looking at the tributes before laying her flowers and reading some of the messages left by others.
She and Mr Hurley hugged. She is understood to have met with first responders in the town earlier.
Speaking to the media today, Southport MP Patrick Hurley said: 'The town is in mourning, the town is in shock this morning. The incident that took place yesterday was uniquely horrific.
'Southport's a quiet seaside, coastal town. This has just sent shockwaves through the whole community. It's a very small town, Southport, and a lot of families across the area will be impacted directly.
'I think at this stage we need to just reach out, make sure that there's a level of community healing going on and make sure we give voice to the solidarity that people need right now.'
Alder Hey children's hospital confirmed today that seven children were taken to their A&E following the stabbing.
Following the announcement of little Bebe's death, her family said in a statement: 'No words can describe the devastation that has hit our family as try to deal with the loss of our little girl Bebe.'
Churchtown Primary School released a statement this afternoon and said: 'Our whole Churchtown Primary School community is utterly heartbroken by the tragic events that have taken place.
'We stand united with all of our families and the wider Southport community during this incredibly difficult time.'
The family of Alice also paid tribute to their 'princess'.
They said: 'Keep smiling and dancing like you love to do our Princess, like we said before to you, you're always our princess and no one would change that. Love from Your Hero Daddy and Mummy.'
Heartbroken relatives of Alice said she had been taken by a 'despicable human being.'
Her mother Alexandra Aguiar is understood to be originally from Caracas in Venezuela and her dad David Aguiar is from the Portuguese island of Madeira.
Portuguese PM Luis Montenegro issued a statement following the death of three children.
He said on X: 'It is with deep sadness that I received the news on the attack that took place yesterday in Southport in the United Kingdom, for which I have no words to describe.
'On my behalf and that of the Portuguese government I express heartfelt condolences to the families of the victims and to the British government and people.'
