Japan on Monday launched a national exercise to encourage tens of thousands of commuters to work from home, in a bid to ease rail and road congestion before the 2020 Tokyo Olympics and reform the country's workaholic culture.

About a quarter of the population of 127 million live in Tokyo and surrounding prefectures.

The congested megalopolis thus faces a serious need to ease rush-hour crowds to accommodate tourists for the Olympics.

The public-private "Telework Day" involved some 60,000 workers at more than 900 companies, organisations and government offices, according to the internal affairs ministry.

They worked from home, skipping their usual habit of commuting in notoriously packed trains or driving personal cars to the office.

The ministry had no figures to break down participation by region but most of those involved are believed to be in Tokyo.

The idea followed a teleworking effort at the time of the 2012 London Olympics. Japan will repeat the exercise on the same date over the next two years in the run-up to the opening of the Summer Games on July 24, 2020.

The plan is also part of Prime Minister Shinzo Abe's efforts to rethink Japan's workaholic tradition, where mostly male workers are routinely expected to spend long hours in the office and have little time with their families.

The government earlier this year unveiled its first-ever initiative to limit overtime in a bid to tackle "karoshi", or death from overwork. It hopes that once the Olympics are over, more people will telecommute as a lasting legacy.

"Teleworking can be one solution" to heavy traffic congestion in the Tokyo metropolitan area, said a government official in charge of the campaign.

"Some people may say they felt some effect (on reducing congestion) this morning, while others say they felt no difference.

"This is a small start but we'd like it to trigger companies as well as workers to start thinking about a different work style," he told AFP .