A teenager has been arrested on suspicion of attempted murder after a child was thrown from the 10th floor of the Tate Modern.
The six-year-old boy landed on the fifth floor balcony of the art gallery. He was air-lifted to hospital in critical condition.
A 17-year-old boy has been arrested in connection with the incident, said Metropolitan Police.
- Minnesota man accused of hurling young boy from mall balcony
- US teacher sacked after literally kicking 11-year-old out of class
"There is nothing to suggest that he is known to the victim," said a statement from police on Sunday.
The London Ambulance told CNN it received the first call about the child at 2.40pm on Sunday afternoon (UK time).
The gallery was placed in lockdown until 5.30pm.
Manchester woman Nancy Barnfield told CNN she was on the 10th floor of the famous gallery when the incident occurred.
She told CNN she heard a loud bang as she was walking away and saw several people restraining a young man.
She said she had previously noticed the man acting suspiciously but he was not resisting.
The Tate Modern is one of London's busiest tourist attractions, drawing crowds of more than five million annually.