Japanese authorities are stepping up surveillance of unlicensed taxis at Narita Airport near Tokyo, as a spike in the number of arrivals increases demand for transport into the capital.

Transport ministry officials handed out hundreds of fliers stating "Beware! Unlicensed taxis are illegal and unsafe!" in English and Chinese to arriving international visitors in early November at the airport in Chiba Prefecture.

The fliers urge people to check the color of vehicle license plates as licensed taxis have green plates or plates with green frames. Unlicensed taxis have the white plates of private vehicles.

It also warns that passengers may not be covered by insurance if injured while riding in an unauthorized taxi.

"To ensure safe travel, we want travelers to use (authorized) taxis and hired vehicles that are well managed," said Mitsuteru Yanase, head of the transport ministry's Chiba branch office.

Unlike overseas where ride-hailing operators, including Uber Technologies and Grab Holdings are widely used, Japan in principle bans such services that enable drivers of private vehicles to serve as unofficial taxis.

Uber and other apps are available in Japan, but they can only be used to call licensed cabs.

Against the backdrop of an acute shortage of taxi drivers in rural areas and tourist spots, however, calls to open up the market grew recently within the ruling Liberal Democratic Party, including from former Prime Minister Yoshihide Suga.

Prime Minister Fumio Kishida also expressed willingness in October to address the problem and vowed to discuss allowing ride-hailing services to operate.

But the transport ministry is cautious and the taxi industry remains opposed to introducing competing services, citing safety concerns linked to the absence of rules on who would be responsible for vehicle maintenance and checking drivers' health.