Tokyo, Dec. 22: A commuter who allegedly groped a college girl on a crowded train collapsed and died after being chased along a platform by fellow passengers.

The 40-year-old office worker fled from the train as it pulled into a station after the student screamed and accused him of groping her bottom and legs.

Four male passengers, including two off-duty policemen, gave chase, bringing him to the ground as he tried to escape. He died later in hospital from a heart attack. The incident took place on the morning rush-hour express on the Hanwa Line into central Osaka ? a spectacularly crowded commuter route that has become one of the most notorious hunting-grounds of Japan’s reviled chikan, or railway gropers.

As the packed carriage pulled into Tennoji station, the student is said to have shrieked loudly, grabbed her alleged chikan by the shoulder and told fellow passengers what had happened. Instead of ignoring her plight, as Japanese commuters routinely do, fellow passengers decided to take the law into their own hands.

The incident has highlighted the widespread problem of groping on trains in Japan. But the ferocity of the other passengers’ reaction has also sounded alarm bells. Male Japanese commuters appear to have been stirred to a new mood of chivalry by a hugely popular TV drama, in which a woman falls in love with the man who rescues her from a drunken chikan.

Until yesterday, that mood had not translated into vigilante-style incidents.

For decades chikan have been the scourge of women commuters and police have been forced to concede that recent drives to stamp out the molesters’ activities have only increased their numbers.

A year ago, an anti-bottom-pinching campaign by the government was declared a disaster after a poll taken in its wake showed that two thirds of young women have been groped on trains at some time.

Even the measure of introducing women-only carriages on many of the most overloaded commuter lines has not significantly affected the figures.

The official numbers for groping are at a record high, with 2,201 reports on the Tokyo underground alone last year and a worrying rise in the number of younger victims.

The figure represents a tripling of incidents since 1996, but police sources said that the levels mask the dramatically higher number of actual attacks, because so many women are too ashamed to speak up, or satisfy themselves by simply slapping their assailant across the face and walking off.

Over the past few years the blight has taken on an even more sinister aspect as chikan across the country have used the internet to organise themselves into efficient “gropers’ guilds”. Chikan exchange tips on the best times and commuter lines to target, and even run interference for each other so that guild members can undertake a particularly brazen attack. The Hanwa Line is a particular favourite of the gropers because it is so crowded at peak times that it is nearly impossible for a victim to work out exactly whose hands are at work.

Blameless male passengers often clasp their books with both hands to assert their rush-hour innocence.

Japan has been slow to deal with the problem of sex crime and the government and police response to combat chikan offenders has been sluggish.

Only belatedly in 2004 was the maximum penalty for molestation raised to seven years imprisonment and a fine of about ?250, and just a handful of cases have properly tested this.