Fishing boats are left frozen in the ice in Dalian, Liaoning province, on Thursday. PHOTOS BY Feng Yongbin, Lyu Wenzheng and HU DUNHUANG

Fishermen in Dalian, Liaoning province, have moored their vessels to prepare for expanding sea ice in coming days.

"But we have still worked to harvest up to 7 metric tons of oysters every day and have taken them to Jinshitan port," said Hu Xinhua, manager of Dalian Jinshitan Port Co.

The cold front brought snowstorms across northern and southern areas on Friday, affecting 90 percent of the country.

The National Meteorological Center issued three alerts to warn local authorities and the public.

Highways in at least 12 provinces and municipalizes were closed and flights disrupted amid blizzards and gales.

Li Ran, a power plant worker in Shijiazhuang, the capital city of Hebei province, said she was stranded for hours on a bus heading for her plant on Friday morning due to slippery roads after snow fell.

Many parts of China are forecast to experience their lowest temperatures in decades during the weekend, with heavy snowstorms expected to persist in eastern and central areas. Blizzards are expected to affect parts of Shanghai and Jiangsu, Zhejiang, Anhui, Hubei and Hunan provinces.

Zhang Yu in Shijiazhuang Zhang Xiaomin in Dalian, Liaoning province contributed to this story.