Police are investigating two shootings, one involving a 14-year-old boy, at the Notting Hill Carnival.
The youngster was injured on Monday night, at the junction of Portnall Road and Harrow Road in Westbourne Park.
Earlier, a 17-year-old was taken to hospital with a shoulder wound after shots were fired. A man in his 20s was injured in a stabbing.
Police said there was a "hardcore" of trouble-makers at the carnival, which attracted 600,000 visitors on Monday.
Officers had maintained a presence to guard against trouble, with about 4,000 deployed for the event. A total of 206 people were arrested over the weekend.
The stabbing was reported at about 1815 BST on Monday at Westbourne Park Road. The victim is in a stable condition in hospital.
Three people arrested on suspicion of attempted murder over a stabbing in Ladbroke Grove are still being questioned by police.
And another three people were arrested in Bayswater Road on suspicion of possession of firearms.
The first shooting happened in the area of Blenheim Crescent. An arrest has been made in connection with the incident, police said.
The 14-year-old was shot in the leg at about 1900 BST.
Forensic science experts have been conducting searches where the incident happened at the junction of Portnall Road and Harrow Road.
It is believed the teenager will be discharged from hospital on Tuesday.
Deputy Assistant Commissioner, Chris Allison, in charge of policing the carnival, said: "Bank holiday Monday saw many thousands join in the event and have a great afternoon out.
"However, what we witnessed from 1700 BST that afternoon shows that there was a hardcore, mainly of young men, who came to carnival not to enjoy the event but to fight, commit crime and cause trouble.
"Our officers had to work hard and deliver a strong interventionist style of policing late into the night to make sure that these criminals were not allowed to take over the streets of Notting Hill.
"Unfortunately, we witnessed groups fighting; objects being thrown at police and large groups of youths pushing roughly through crowds.
"Two young men were shot, fortunately not seriously injured, and a small number of people suffered minor stab wounds.
"No one wants to see this unique event being overshadowed by such unacceptable behaviour."
The carnival, now in its 43rd year, is the world's second largest street party after the Rio Carnival held in Brazil. An estimated 1.4m people attended on Sunday.
Processions of brightly-dressed participants in elaborate costumes danced along west London's streets to the sound of Caribbean rhythms.
Carnival-goers had praised organisers and police for making the event feel safe.
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