Typhoon Champi nears Taiwan, causing flight cancellations and disrupting US-Japan drills

Taiwan issued a land warning on Thursday as powerful Typhoon Champi approached, prompting more than 200 flight cancellations in the region and forcing changes to a major US-Japan military exercise.

At one point a super typhoon and one of the strongest storms in the Pacific this year, Champi weakened slightly on Thursday but was still packing gusts of more than 227 kph near its centre, according to Taiwan's Central Weather Administration (CWA).

The storm was about 520 km southeast of Taiwan's southern tip, the CWA said. The storm's track shows it will pass northeastern Taiwan, turn north toward the Chinese coast and eventually move into southern Japan.

The administration said its radius expanded slightly to 320 km, large enough to cover most of Taiwan, and weather experts said its impact could last nearly two days.

Coastal towns received mobile phone alerts warning of waves exceeding 6 metres, while nearly a metre of rain was forecast in northern mountain areas, including the hills near Taipei.

Taiwan's President Lai Ching-te called for the public to get ready now for the typhoon, and avoid going to the mountains or the coast.

"A little more preparation means less risk," he wrote on his Facebook page.

Taiwan's transport ministry said 125 flights had been cancelled on Thursday, mostly domestic ones, though the rail network was so far unaffected. The interior ministry said no evacuations of residents had yet been reported.

Taiwan is generally very well prepared for typhoons, which keeps casualties low. Although more common in summer, the storms can strike in autumn, bringing strong winds and torrential rain.

The typhoon is also forecast to pass over Japan's westernmost inhabited island, Yonaguni, in Okinawa Prefecture.

In Japan, major carriers Japan Airlines, ANA and Skymark have cancelled more than 100 flights, mostly domestic, between Thursday and Sunday, disrupting travel for over 11,000 passengers.

The approaching storm is also disrupting the major military exercise called Keen Sword that is underway around Japanese islands near Taiwan.

Held every two years, the exercise rehearses Japan's defence through coordinated land, sea and air operations, including missile defence drills and amphibious landings. It began on Monday, involving about 56,000 Japanese and US personnel alongside forces from five other countries, including the Philippines and Australia.

"Training activities are being adjusted on a day-to-day basis to ensure the safety of all participants," the US military said.