Usagi is to hammer China's Pearl River Delta some time between Sunday afternoon and Monday morning. Southern coastal provinces have evacuated residents, issued alerts, canceled air and shipping services. 21 (Xinhua) -- Southern Chinese coastal provinces have evacuated residents, issued alerts and canceled air and shipping services as super typhoon Usagi strengthens over the Pacific and moves towards China. Usagi is expected to hammer south China's Pearl River Delta some time between Sunday afternoon and Monday morning. Usagi was 660 km southeast of Hong Kong at 5 p.m. Saturday, packing a wind speed of 187 km per hour at its center. It was moving northwest at a speed of up to 20 km per hour, the National Meteorological Center said in a latest update. The agency issued the highest level of alert for Usagi, warning that it will bring gales and downpours to southern and southeastern coastal areas. China Southern Airlines said it would cancel flights in and out of Hong Kong on Sunday and cancel flights to Shantou, Zhuhai and Shenzhen in the Pearl River delta as of 10 a.m. Sunday as local airports could be battered by heavy rains and strong gales starting Sunday noon. The airlines would notify affected passengers through phone calls, text messages and emails, it said. Meanwhile, the Baiyun International Airport in Guangzhou, the capital city of Guangdong, has issued a yellow alert over the approaching typhoon and stepped up support measures to guarantee safety and deal with emergencies. Meanwhile, Guangdong's neighboring Fujian Province has evacuated more than 80,000 people and deployed over 50,000 disaster-relief personnel.