At least 43 people, including a young child, have been killed after a bus and lorry burst into flames in a head-on crash in France.

Motorists desperately tried to smash windows of the burning bus to free passengers near Bordeaux, southwestern France.

Most of the victims were French pensioners going on a day trip to walk in the wine-producing region of Bearn.

Among the dead were the wood lorry driver and his three-year-old son, sources in France reported.

It has emerged that the boy was only discovered some time after the crash, after relatives told authorities he must have been in the truck.

The accident happened at around 7.30am in the Gironde area, about 60km (35 miles) from Bordeaux in the town of Puisseguin.

Witnesses said the vehicles collided on a dangerous bend - and described the aftermath as "like a war zone".

A doctor at the scene told how some survivors lay on the side of the road, while others were in shock, covered in blankets.

An image released by BFM television showed the carcass of the bus - nothing but a collapsing, charred frame engulfed by smoke.

Helicopters evacuated severely burned victims, and scores of emergency workers were at the scene.

Eight people escaped from the bus. Three are seriously hurt, while the other five have minor injuries.

The bus driver was among the injured. He was taken to hospital, but is now being questioned by officials, as a witness.

Dr Philippe Flipot told Le Parisien newspaper how he spoke to the bus driver at the scene.

"I saw the bus driver at the scene and he was in shock. He told me he was unable to avoid a jack-knifed lorry but managed to open the doors for passengers to escape," he said.

"He was also forced to flee the bus to escape the flames - but managed to evacuate some of the passengers."

Dr Flipot, who said some survivors had been badly burned, added that he treated several passengers, including an elderly lady.

"She told me that she was just so glad to have survived - then she burst into tears," the doctor said.

It is the most deadly road accident in France since 53 people, mostly children, died in a bus crash in Burgundy in July 1982.

A witness who was at the scene soon after the crash said: "I saw a huge, very large, and very intense plume of smoke.

"It was astonishing. Then I saw a police car and, straight after, fire engines everywhere.

"It seemed to me like a war zone and that's not saying it enough. Then, I moved forward on the road and I could tell it was something serious."

The town has been closed off while bodies are removed.

The mayor of nearby Petit-Palais, where many of the victims lived, has lost three members of her family, it has emerged.

President Francois Hollande, who is in Greece, said the French government was "totally moved by this terrible tragedy".