East Japan Railway Co. said Tuesday it will introduce security cameras on trains running on Tokyo's Yamanote loop line to enhance security.

The railway operator said it will introduce the cameras on 550 train cars starting in the spring of 2018, completing installation by 2020 in time for the Tokyo Olympics.

The measure is expected to cost around ¥2 billion, according to the company.

"Crimes and nuisance are becoming noticeable on trains. (Cameras) are necessary to prevent terrorism as well," President Tetsuro Tomita said at a news conference, adding that there are plans to equip train cars on other JR East lines with cameras as well.

The cameras will be placed near display panels above doors. JR East said it will take necessary measures in accordance with its company codes and relevant laws to protect the privacy of passengers.

Like some other lines in the capital, the Yamanote Line, which carries more than 1 million passengers per day on average, has become notorious for groping incidents during the morning and evening rush hours.

Tomita said JR East plans to notify passengers when security cameras are in operation by posting stickers. It will store footage for about a week but allow a only limited number of employees to access the video data due to privacy concerns.

Trains on a few bullet train lines have introduced regular video recording in passenger cabins. Some private railway operators such as Tokyu Corp. and Tokyo Metro Co. have decided to install security cameras on all their train cars.