Media playback is unsupported on your device Media caption CCTV pictures from inside the tunnel show rescue workers scrambling over huge slabs of concrete

A major road tunnel has collapsed in Japan, trapping a number of vehicles and leaving at least seven people missing, media reports say.

Survivors described how large sections of concrete fell on top of cars in the Sasago tunnel.

A fire broke out and rescuers have found a number of charred bodies.

The incident started at 08:00 local time (23:00 GMT Saturday), about 80km (50 miles) west of Tokyo on a road that links it to the city of Nagoya.

The tunnel is one of the longest in Japan.

'Frightened'

Pictures from closed circuit TV cameras inside the tunnel showed a section of up to 100m (328ft) that had caved in on the Tokyo-bound lanes on the Chuo Expressway in Yamanashi prefecture.

Image copyright Reuters/Kyodo Image caption Smoke was seen billowing from the Sasago tunnel In pictures: Japan tunnel collapse

Thick black smoke blew out of the tunnel, hampering the rescue, which had to be suspended for several hours because a further collapse was feared.

When it resumed, the first fatalities were found.

A spokesman for Yamanashi Prefectural Police told Agence France-Presse: "A number of charred bodies were confirmed inside. The number of dead is not known."

A lorry driver who had managed to call for help was one of those reported to have died.

The BBC's Rupert Wingfield Hayes, in Tokyo, says CCTV pictures now show rescuers moving freely over the collapsed roof sections.

He says there has already been criticism of the rescue services, which media say took three hours to reach the collapse site.

One woman who made her way out of the tunnel said she was with five other people in a van, but added: "I have no idea about what happened to the others. I don't know how many vehicles were ahead and behind ours."

A reporter for the NHK broadcaster described driving through the tunnel as it began to collapse, seeing other cars trapped and on fire. His car was badly damaged, he said.

Another survivor told the broadcaster that he saw "a concrete part of the ceiling fall off all of a sudden when I was driving inside. I saw a fire coming from a crushed car".

Survivor Tomohiro Suzuki said: "A part of the ceiling, just as wide as the road, had collapsed straight down and broken in the middle into a V-shape."

He and his family walked for an hour to get out, with the smoke worsening.

"I heard after a while on the public address system that a fire had occurred inside the tunnel and the sprinkler system was going to be activated," he told Jiji Press.

"I kept wondering when the fire would spread and catch us," Mr Suzuki said.

The twin-bore Sasago tunnel is an estimated 4.3km (2.7 miles) long and is on one of the major highways out of Tokyo.

The road has had to be closed because of the seriousness of the accident.

Our correspondent says there will be serious question about how a major tunnel on one of Japan's most important traffic arteries could have failed so catastrophically, with the private company that runs the highway saying the tunnel had undergone a major inspection just two months ago and had been given a clean bill of health.

Japan is prone to large earthquakes, but none were reported in the area in the morning.

Motohiro Takamisawa, of the highway's operator, Nexco, said he believed structural failure was to blame.

He told Reuters: "Between the two concrete plates, there's something that supports them. It does appear that is what actually collapsed, but that is just judging from security camera footage."