Welsh plane crash: Teenage girls among the dead
Two teenage girl Air Corps cadets and their RAF trainers were the four onbaord the two planes that collided mid-air into each in the sky near Porthcawl, Wales.
The wreckage is spread over about half a mile and police have been receiving reports from members of public coming across the debris.
One of the twin-seater planes was on fire when emergency services reached the scene.
The two planes are from a flight training school at the RAF base in Cranwell, Lincolnshire.
Local resident Reena Callingham said to a reporter on BBC news:
"I just couldn't believe it. At first there wasn't an explosion straight away but then there was. They just went down," she said.
Supt Tim Jones, of South Wales Police, said: "There are believed to be a total of four fatalities.
"I hope you all understand at this time our priority is to talk to members of the family and next of kin and we are working together to support them at this most difficult time.
"A major incident room has been set up at police headquarters in Bridgend and a response is being co-ordinated from there."
The identities of the people who have died have not yet been revealed.
A number of helicopters were used during the incident to gather evidence and mountain rescue teams were on stand-by.
The inquiries will be undertaken by police, Ministry of Defence and the Air Accident Investigation Branch (AAIB).
Four people have been killed in a mid-air collision between two aircraft near the south Wales coast.
They died near the seaside resort of Porthcawl at around 1100 GMT. Their identities have not been revealed.
The wreckage was spread over about half a mile, with some in sand dunes near Kenfig nature reserve.
The two aircraft were from the flight training school based at RAF Cranwell in Lincolnshire. Two separate inquiries are under way into the crash.
One eyewitness told the BBC she saw two planes hit each other in the sky, before she heard an explosion.