An Iranian man set himself on fire in central London during a political protest outside the French Embassy.
Police found a fire extinguisher at the scene
The man is thought to have doused himself in petrol outside the embassy in Knightsbridge at 1615 BST on Tuesday.
He was taken to the Chelsea and Westminster Hospital suffering 40% burns and is said to be in a serious condition, although it is thought he will survive.
Others were treated for minor burns, thought to be received when they tried to extinguish the flames.
Up to 60 people were protesting outside the embassy following a raid by police in Paris on the Iranian opposition group the People's Mujahideen - declared a terrorist group by the US.
More than 150 people were arrested following the raid, in which more than one million US dollars were seized.
Scotland Yard said the protest started peacefully, but more police had to be called in at 1500 BST as the crowd became "more volatile" and pushed through police lines.
Everyone has a right to protest but this man felt it necessary to set himself on fire
Phane Gompertz, French Embassy
Officers wearing protective clothing used powers under the Public Order Act to search the remaining protesters.
Protester Laila Jazayeri said: "This Iranian man has set his life on fire to tell the world to condemn the actions of the French police and French government.
"The arrests come just when in Iran we are witnessing demonstrations by students who are saying no to the regime there."
Phane Gompertz, from the embassy, said: "Everyone has a right to protest but this man felt it necessary to set himself on fire.
"We only hope that his condition is not too bad."