Fifteen men were burned or choked to death and at least 10 more injured when a "video house" in the heart of central Osaka was engulfed in flames, trapping customers in a terrifying maze of flimsy wooden partitions.

As the blaze tore through the building in the early hours of Wednesday morning, the all-male clientele of the Cats video house began a hopeless stampede for the exit along its pitch-black corridors.

The blaze, which broke out in one of the establishment's 32 cramped ground-floor cubicles, was initially thought to have been an accident with a cigarette, but police say they now suspect arson. A man in his 40s, who was renting the cubicle where the fire began, is currently being questioned in connection with Japan's deadliest blaze for seven years.

Most customers were sound asleep when the fire began, and of the 15 dead, the majority appears to have died from carbon monoxide poisoning long before they could reach the doors. Survivors say that there was no attempt by any of the shop's staff to help customers escape the inferno, and that the corridors - already too narrow for more than one person to pass along at once - were cluttered to shoulder-height with cardboard boxes and other rubbish.

One 37-year old customer was awake and watching videos when he smelled the smoke and charged out of his room. He described clouds of white smoke belching through the corridors and the sounds of screaming and panic from some of the other rooms.

Another regular customer, aged 22, said that he had never actually seen an emergency exit in the place, and that it would have been impossible for those furthest from the main entrance to navigate the corridors in the dark.

The deadly inferno has dramatically exposed the murky world of Japan's video houses and so-called "manga kissa" - the comic and video libraries that hire out small cubicles by the hour but have instead taken on the function of ultra-cheap hotels and, in some cases, brothels.

The shops, of which there are now dozens in every major city in Japan, have become potent symbols of the "hidden poverty" lurking just beneath the surface of the world's second biggest economy. When the manga kissa and video houses first surfaced a decade ago, they would always have a few people spending the night there - mainly people who had stayed out late beyond the last train.

But as Japan's once monolithic middle class has polarised into two classes of economic winners and losers, the comic cafes and similar establishments have been seized upon as little more than convenient doss houses.

Customers pay around 1,500yen (£7.50) for a night's stay in a 2m x 1m cubicle with a small sofa and either a collection of manga comics or a television and a collection of adult videos. A large number maintain direct links with the sex industry and allow customers to have girls sent to their cubicles by local "delivery health" services.

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