Tokyo's trains can be very crowded at rush hour

A railway company in Japan is to install special cameras on its Tokyo commuter trains to help deal with the problem of groping on public transport.

The cameras are to be fixed on the ceiling of carriages on the Saikyo line, which is known for attracting sexual predators.

Some 2,000 complaints for groping are filed with Tokyo police every year.

In a survey, four in five women report being molested on public transport, and some trains have women-only carriages.

The planned cameras will be fixed on carriage ceilings or overhead racks in a pilot project as early as this month.

Gropers' recommendations

Signs will advise travellers that they are under surveillance, according to a spokesman for the East Japan Railway company.

Sexual harassment has been a significant problem on Japan's trains for years.

More than 6,000 people were arrested last year on suspicion of groping or taking unsolicited photographs.

Several suspects arrested in recent months are said to have told officers they had targeted particular train lines because of recommendations they had read on websites.

Train gropers - or chikan - are common characters in Japanese popular culture.