Reported incidents of sexual assault on Tokyo's trains have reached a record high, with 2,201 cases last year.
Police called for more women-only train carriages
This is up from 2,058 cases in 2003 and is triple the number of such incidents recorded in 1996.
The rise is partly attributed to the increased willingness among women to report assaults.
A recent survey found that nearly 64% of Japanese women in their 20s and 30s said they had been groped on trains, subways or at stations in Tokyo.
More than half of the incidents took place during morning rush hour, when passengers are pressed tightly against each other, police said. Teenage girls accounted for a third of the victims.
Groping has long been a problem in Japanese trains, and a few lines have introduced women-only carriages.
The police said they planned to step up patrols on trains and platforms and urge rail companies to increase the number of single-sex train cars.
Reporting culprits has been made easier by the introduction of mobile phones with a camera facility, which allow the victim to take a photo of the molester.