The death toll from the strongest storm to hit China in four decades has reached 18, state media said as forecasters issued warnings of more extreme weather.

Typhoon Rammasun has left eight people dead in the island province of Hainan and another nine in Guangxi, official news agency Xinhua reported on Sunday.

At least two people were missing, Xinhua added, citing local authorities, as the strongest typhoon to hit south China since 1973 headed north.

Television pictures on Sunday showed waterlogged roads and heavy rain in the southwestern province of Yunnan.

Online pictures showed uprooted trees, destroyed crops and deserted, rain-soaked streets across much of southern China.

Super typhoon

The typhoon first made landfall in China on Friday afternoon as a super typhoon, packing winds exceeding 200km/h.

Weather authorities in China issued a "red" alert warning for Rammasun on Saturday - the most severe of China's four colour-coded warnings.

But the storm has since been downgraded "as it is abating and affecting fewer Chinese localities", Xinhua added.

All the airports on Hainan had re-opened on Sunday, as ferry, rail and bus services resumed, it said.

Meanwhile, China's National Meteorological Centre was warning that downpours triggered by the typhoon were expected in northern parts of China in the coming days.

Rammasun, meaning "Thunder God" in Thai, has caused at least 94 deaths in the Philippines, where it hit before lashing China.