Train passengers will soon be able to use their mobile phones on the city's subways.

Japan's three largest mobile carriers said Wednesday that they would begin to offer services on sections of some lines from this week, with full coverage to come later this year. Voice and data will be available in stations as well as underground tunnels.

NTT DoCoMo, KDDI, and Softbank said in a joint statement that the first section to go live will be a stretch that runs from Shinjuku, a central business and shopping district. EMobile, which mainly offers high-speed data services, is also participating.

Tokyo's miles of subways, some of which run several stories underground, have long been a rare gap in the city's blanket cellular coverage. Commuters often scramble to make calls, download their messages, and check train schedules during brief stops at the stations where they get reception.

Some are concerned that mobile services on subways will end a rare sanctuary from the constant background of phone chatter in the city. Posters on trains ask that passengers refrain from making calls on trains and switch their ring tones to vibration mode. In the joint announcement for the start of services, Japanese carriers asked that train passengers "continue to observe the rules for using mobile phones, as they have in the past."