At least 42 people have been killed in a head-on collision between a lorry and a bus near Bordeaux in southwest France.

The victims were French pensioners going on a day trip to walk in the wine producing region of Bearn. The crash happened at around 7.30am in the Gironde area about 60km (35 miles) from Bordeaux in the town of Puisseguin.

Witnesses said the crash happened on a dangerous bend and described the aftermath as like a war zone. It is the most deadly road accident in France since 53 people, mostly children, died in a bus crash in Burgundy in July 1982.

The bus was about 20 minutes into its trip and the impact was so fierce that both vehicles burst into flames, trapping the majority of those inside. An image released by BFM television showed the carcass of the bus – nothing but a collapsing, charred frame engulfed by smoke.

Eight people escaped from the bus after the driver somehow opened the door. Puisseguin Mayor Xavier Sublett said that the truck driver lost control.

The bus driver tried to avoid it, but the truck came and hit it, and he couldn’t do anything except activate the mechanism to open the doors to allow some people to get out, Mr Sublett said.

An eyewitness who was at the scene soon after 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, Patricia Raichin, is one of those directly affected by the tragedy – she has lost three members of her family. The president of the hiking club in Petit-Palais, where many of the passengers lived, said the group was planning a walking trip.

President Francois Hollande, who is in Greece, said the French government was totally moved by this terrible tragedy. Prime Minister Manuel Valls and other senior government ministers are on their way to the site of the crash.

It is France’s worst road accident since 1982 when 53 people, including 44 children, died in Beaune in Cote-d’Or.