South Korea was Monday bracing for major typhoon Bolaven, with a main port and ferry routes closed, classes cancelled, a military exercise suspended and officials put on high alert.

Typhoon Bolaven -- one of the region's most powerful storms in decades -- was churning towards the peninsula after lashing Japan's Okinawa island with heavy rain and wind, knocking out power, and injuring at least five people.

One man died on Japan's nearby island of Amami, Kagoshima prefecture, after being swept away by a swollen river, the Kyodo news agency reported.

The typhoon, with winds of up to 173 kilometres (107 miles) per hour, was expected to hit South Korea from late Monday to early Wednesday before reaching North Korea, Seoul's weather service said.

A joint military exercise with the US has been suspended until weather conditions improve, the Combined Forces Command said in a statement, according to the Yonhap news agency.

South Korea's defence ministry earlier said personnel in the path of the typhoon had been ordered to take shelter and move planes and ships to safer areas.

In the southern port city of Busan authorities Monday banned all ships from entering the docks until the storm passes. Large ships were advised to move elsewhere out of the storm's path.

The transportation ministry said 68 of the country's 87 sea ferry routes had been cancelled. Airport authorities were checking runways and other facilities.

A state disaster relief board raised its alert to the highest level, meaning more officials will be on watch.

Some 140 flights on Monday and Tuesday, mostly to or from the southern resort island of Jeju, were cancelled.

President Lee Myung-Bak called for "thorough preparation" to minimise damage and prevent casualties.

In Seoul and the western port city of Incheon, all schools were ordered closed Tuesday.

The typhoon will dump as much as 500 millimetres (20 inches) of rain in some parts of the nation from Monday to Wednesday and bring strong winds and high tides, the weather service said.

Storm alerts will be issued in most parts of the country by Monday night.