Horrified witnesses have described seeing a boy carrying a "massive" carving knife after four teenagers were stabbed on a south London housing estate.
One boy is in a critical condition and another is seriously ill after the attack on Thursday evening.
Residents on the estate in Camberwell, close to where a drill rapper was stabbed to death earlier this month, said they saw a group of up to 30 boys.
One local mother, who did not want to be named, said she saw one of the boys carrying a blade more than a foot long.
"I could see the knife in his hand, I could clearly see the blade, it was big and that was worrying me," she added.
"My little boy is growing up around here, it's terrifying."
Another witness said she saw "lots of blood" on the ground and saw a "massive" knife lying on the floor.
"I did see a massive blade, a carving knife, it was horrifying," she added and gestured that the weapon was more than a foot long.
Scotland Yard said the victims of the latest incident were between 15 and 16 years old.
Another resident, who also did not want to be identified, said she dialled 999 after one of the boys fell to the floor clutching his side.
"I saw a boy holding his side and he just fell on the floor so I called the police," she added.
"I was really shaken up, you could see the bloody clothes and from window."
She said the incident happened outside her young daughter's bedroom and added: "I hate it here, it's getting worse and worse. I'm frightened to go out the front door.
"As frightened as I was, I wasn't going to let someone die in front of me."
A group of boys were seen running outside Landor House on the Elmington Estate minutes before police arrived at around 5.30pm.
A neighbour said he saw one of them jump from a first floor balcony and added: "There was a gang of 20 maybe 30 and they were running back and forth.
"I saw one jump from a balcony and ran across towards the shop area."
Six boys aged between 15 and 16 are in custody after being arrested on suspicion of violent disorder and grievous bodily harm, Scotland Yard said.
A mother-of-four who lives on the estate said she saw some of the group being arrested.
"I saw police chasing people, four officers had to grab this one boy," she added. "He was fighting one (officer) and three others had to get involved.
"I don't let my kids out to play, if I'm not there they're not going out."
A crime scene remained in place on Friday afternoon and the police helicopter could be seen circling overhead.
The estate - which was littered with bloodied clothing, trainers and medical equipment - is just a short walk from Warham Street, where 23-year-old drill rapper Sidique Kamara, also known as Incognito, was stabbed to death on August 1.
A man, who asked not to be named, said he saw one of the victims "holding his belly and all of his intestines were falling on the ground".