A mother and two children were among six people hurt in a collision in Canterbury, police have said.
Kent Police said a silver Ford Mondeo and a blue Toyota were involved in the accident in Broadoak Road at 1507 GMT.
A spokeswoman said a four-year-old girl and a male passenger in the Mondeo were taken to a London hospital with life-threatening injuries.
Also travelling in the Mondeo was a six-year-old boy and the children's mother.
They were taken to the Queen Elizabeth the Queen Mother Hospital at Margate.
A force spokeswoman said their injuries were not believed to be life-threatening.
The occupants of the Toyota, a 16-year-old passenger and a female driver, received non-life threatening injuries.
The road was closed while police carry out an investigation.