Two 15-year-old boys and a 16-year-old are among four people stabbed at the Children's Day Parade of the Notting Hill Carnival in London.
Four stabbings took place on the first day of the annual event celebrating Afro-Caribbean culture in London's west that is traditionally a family-orientated event.
The three teens along with a 20-year-old man, who was also stabbed, were taken to hospital in a critical condition which was later deemed to be non-life threatening.
More than 100 arrests were made at the event that is expected to attract up to one million people over two days during the August bank holiday weekend.
Nearly one quarter of the arrests were for possession of a bladed weapon while 74 were for drug offences.
The London Ambulance Service also reported more than 411 people had been treated, 77 of whom were taken to hospital.
The colourful annual parade was started in 1966 by West Indian immigrants to the area after race riots in 1958. Huge swathes of the suburb are blocked off over two days to make way for food stalls, bars and carnival trucks with sound systems pumping from the back.
However the carnival also has a reputation for being marred by violence on the fringes. This year, London's Met police debuted a facial recognition technology system to identify offenders.
That's in conjunction with their elite team of "super recognisers" monitoring the crowd from CCTV to scan for those banned from the event.
Met Police Carnival spokeswoman Superintendent Robyn Williams said: "The technology involves the use of overt cameras which scan the faces of those passing by and flag up potential matches against a database of custody images.
"The database has been populated with images of individuals who are forbidden from attending carnival, as well as individuals wanted by police who it is believed may attend carnival to commit offences."
Check out some of the best pictures from the event below.