BORDEAUX (AFP) - At least 43 people were killed when a coach carrying elderly day-trippers collided with a lorry and burst into flames in south-west France on Friday, in the country's worst road accident for three decades.

The coach was carrying members of a pensioners' club on an excursion when it was involved in a crash with the lorry near the village of Puisseguin among the vineyards of the St Emilion region, east of Bordeaux.

Many of the victims were thought to have died in the fire, according to emergency workers and local authorities.

The lorry driver was also killed along with his three-year-old son who was sitting beside him, said the local police chief.

French television pictures showed the coach was completely burned out, leaving only a charred shell.

"The driver of the lorry appears to have lost control of his vehicle, leaving him stranded in the middle of the road. The bus driver was unable to avoid the accident," Puisseguin mayor Xavier Sublett told reporters.

Locals saw a plume of smoke from several kilometres away. Many said that part of the road was known to be particularly dangerous.

"I am astonished at the force of the crash. It will take a lot of time to recover all the bodies," said a fireman at the scene.

Eight people, including the coach driver, managed to escape the burning wreckage. Four of the survivors were seriously injured with burns or head injuries, according to a local official.

"The bus driver was lightly injured. He had the presence of mind to open the doors to allow as many passengers as possible to leave the bus," said Sublett.

"At the risk of his own life, because the flames were burning him, he managed to evacuate a few people."

The crash is the deadliest in France since August 1982, when 53 people including 44 children were killed in a motorway pile-up.

"The French government has fully mobilised after this terrible tragedy," President Francois Hollande said from Athens, where he was on an official visit.

"We are plunged into sadness due to this drama."

Some 20 fire engines and 60 firefighters were dispatched to the scene on Friday, supported by helicopters. A trauma counselling unit and an information hotline were also set up.

Prime Minister Manuel Valls, Interior Minister Bernard Cazeneuve and Transport Minister Alain Vidalies travelled to the site, and the National Assembly, or lower house of parliament, observed a minute's silence.

"It's a terrible shock for France," said Valls.

'AN INCREDIBLE TRAGEDY'

The coach, carrying 48 passengers and the driver, had just departed from Petit-Palais-Cornemps, a village of 650 residents near the scene of the accident.

"It's an incredible tragedy with an extremely heavy toll. It's a catastrophe," Pierre Henri-Brandet, spokesman for the interior ministry, told BFMTV.

"They were retired people, elderly people, who were going on a day out."

The group had been heading south to the nearby region of Landes to visit an outlet specialising in Bayonne ham, a local delicacy.

"We are very affected because all the people on the bus came from the villages in the area," said Jacque Deval, whose brother-in-law and sister-in-law were among the injured.

"My mother and my father-in-law were on the bus. I have just arrived, I don't have any news for the moment, but I'm very scared that they will be on the list of victims," said Delphine Guerineau.

Police said they had yet to remove any of the bodies from the bus by Friday afternoon, and would start identifying victims on Saturday morning.