By Liz Lee and Ella Cao

BEIJING (Reuters) -China on Wednesday dispatched thousands of rescue workers to Zhuozhou, a flooded city of over 600,000 residents southwest of Beijing, as the remnants of Typhoon Doksuri continued to wreak havoc on swathes of the city twice the size of Paris.

Zhuozhou is in Hebei province, which has borne the brunt of the worst storms to hit northern China in over a decade, killing least 20 people. The city also borders Beijing, which was inundated with the most rainfall in 140 years between Saturday and early Wednesday, official data showed.

Authorities in Hebei have declared a state of emergency as rainfall averaged 355 mm (14 inches) since Saturday, the heaviest since at least July 2012. More than 134,000 Zhuozhou residents have been affected, with over one-sixth of the city's population evacuated.

At the confluence of several rivers, Zhuozhou is one of the hardest hit cities in Hebei as floodwaters migrated downstream, according to state media, waterlogging residential areas more than twice the size of the French capital, and affecting nearly 650 hectares of agricultural land.

The local public security bureau said on Tuesday the city faced water shortages and a partial power outage, adding that it urgently needed rafts, life jackets and emergency supplies. Residents said waters rose as high as four metres (13 ft).

Some 9,000 rescuers have been dispatched to Zhuozhou, with more rescue teams rushing over from neighbouring Henan and Shanxi provinces, state broadcaster CCTV reported.

A satellite image taken on Tuesday showed Zhuozhou surrounded by floodwaters on three sides. The Global Times newspaper reported that a large amount of water was flowing from Beijing into three rivers around Zhuozhou.

Many Zhuozhou residents took to social media to complain about how long rescue and recovery efforts were taking. "We are taking on the flood water discharge from Beijing, so they should provide us with rescue and equipment, but there has been nothing," a netizen vented on China's popular microblog Weibo.

Floods have also hit warehouses in the city, a logistics hub. Hebei authorities said they had opened another flood diversion area in Yongding River on Wednesday to help ease the flooding.

BooksChina.com, an online bookstore, said on its WeChat account on Tuesday night their staff were waiting for rescue workers on the fourth floor of their flooded warehouse where over four million books were stored.

As the floodwaters flow south, the authorities in the city of Gaobeidian have evacuated 113,000 residents, as well as opened reservoirs to trap the excess water, Xinhua reported.

In Japan, a typhoon has also struck its southwestern Okinawa prefecture. The storm is expected to veer westwards in the East China Sea, but then turn northeast, potentially towards Japan's third largest island Kyushu.

(Reporting by Liz Lee, Ryan Woo, Ella Cao and Beijing and Shanghai newsroom; Editing by Miral Fahmy)