The Qiongzhou Strait between the Chinese mainland and Hainan island was closed Wednesday as tropical storm Chanthu headed towards south China, said local maritime authorities.

Fishing vessels anchor at Xingang Port to take shelter from the approaching tropical storm Chanthu in Haikou, capital of south China's Hainan Province, July 21, 2010. The tropical storm Chanthu is expected to land onto the coastal areas from Yangjiang of south China's Guangdong Province to Wanning of south China's Hainan Province on July 22. [Hou Jiansen/Xinhua]

The strait was closed to shipping at 10 a.m., said a spokesperson with the Haikou Maritime Bureau.

Chanthu, which was 280 km southeast of the island at 8 a.m., was moving northwestward at a speed of 15 to 20 km per hour, according to Hainan Provincial Meteorological Center.

It is expected to land between Guangdong's coastal city of Yangjiang and Hainan's Qionghai City sometime Thursday, according to the center.

Hainan's Haikou Maritime Bureau made the decision to close the strait after consulting Guangdong's Xuwen Maritime Office.