Around 40 people are believed to have been killed after a huge forest fire swept through northern Israel.

Israeli television showed pictures of a gutted bus and car that were apparently engulfed by the blaze in the Carmel Forest, near the city of Haifa.

Reports suggest many of those killed were prison guards trapped in the bus.

"It's a disaster on a scale that we have never seen before," Israeli Prime Minister Benjamin Netanyahu said.

"We are harnessing all the forces of the state to deal with this disaster and rescue those who are injured and to stop the fire," he added. He later called on Greece, Italy, Cyprus and Russia to help Israel tackle the inferno.

Israeli media said it was the biggest forest fire in the country's history, with 7,000 acres (2,800 hectares) of land destroyed and firecrews struggling to contain the disaster.

Officials evacuated a prison where Palestinian detainees are normally held and the dead guards were believed to have been at the jail when the blaze took hold.

A security source said the driver of the bus crashed attempting to flee the area, giving his passengers no chance to escape the raging fire.

Israeli media said the fire might have started in an illegal dumping ground in the Carmel region.

Israel has experienced unseasonably hot weather for months and it was the driest November in 60 years, meaning the flames were able to spread quickly through the tinder-dry countryside.