A cold wave brought by an air mass of record-low temperatures gripped Hokkaido on Friday, causing traffic disruptions on the northernmost Japanese mainland.

As temperatures plunged below minus 20 C in some parts of the region, the Japan Meteorological Agency also predicted snowfall on Saturday in eastern Japan, with central Tokyo expected to see 5 to 10 centimeters.

The agency said a cold air mass of minus 24.4 C, the lowest since it began compiling data in 1957, was hovering about 1,500 meters above Sapporo, the capital of Hokkaido, where the mercury dropped to minus 12.5 C in the morning.

The annual Sapporo Snow Festival, one of Japan's most celebrated winter events, has been underway since Monday, with visitors having to protect themselves against the cold.

The temperature in the town of Oketo, nearly 200 kilometers east of Sapporo, sank to minus 22.7 C in the early hours of Friday, with that in Rikubetsu town, adjacent to Oketo, hitting minus 20.3 C, prompting the agency to issue warnings about outdoor activities, water pipes freezing and crop management.

Hokkaido Railway Co. said it has suspended 74 train services as of 12:45 p.m. Friday, with some brakes and rail switching points frozen.

A bus connecting Sapporo and Wakkanai, a northern Hokkaido city, slid off the road shortly after midnight due to an apparent whiteout which blocked the view. No injuries were reported among the 25 passengers and the driver, police said.