Severe floods "seen around once a century" are expected to hit parts of southern China, state media said Sunday, as heavy rains prompted authorities to step up disaster precautions.

Torrential downpours have struck swathes of Guangdong province since Thursday, swelling waterways in the Pearl River Delta, China's manufacturing heartland.

Weather alerts are in place across large parts of central Guangdong, with the national weather office warning of major storms in coastal areas through Sunday evening and into Monday.

Aerial footage by state broadcaster CCTV on Sunday showed murky flood waters lapping close to street level in some towns, leaving low-lying buildings inundated and a towering pagoda protruding from the deluge.

Citing the provincial hydrology bureau, CCTV said three locations in the Bei River basin would "experience flooding seen around once a century... due to the impact of heavy precipitation".

Floods of up to 5.8 metres (19 feet) above the warning limit would strike the areas starting early Monday morning, according to CCTV.

Several other places would endure the kind of floods seen once every 50 years, it said.

The Pearl River Delta is one of the most densely populated parts of China, with Guangdong alone home to around 127 million people.

There were no immediate reports of casualties or mass evacuations.

Authorities have launched a level-three emergency response in Guangdong, the second lowest in a four-tier system, according to CCTV.

Parts of the adjacent provinces of Jiangxi and Fujian were also forecast to see severe rainstorms on Sunday evening.

China is no stranger to extreme weather but recent years have seen the country whiplashed by severe floods, grinding droughts and record heat.

Climate change driven by human-emitted greenhouse gases makes extreme weather events more frequent and intense and China is the world's biggest emitter.