The National Search and Rescue Centre's alert carried by the Voice of Vietnam station said the fishermen aboard 11 ships last made radio contact on Wednesday morning as they were some 300 km (160 nautical miles) south of Hainan island on the typhoon path.

Vietnam has alerted all ships in the nearby areas to search for the fishermen, the state-run radio said.

China evacuated more than 600,000 people before Chanchu, packing winds up to 170 kph (106 mph), made landfall in the southern coast on Thursday. The typhoon was advancing northeast, the Hong Kong Observatory said.

In the Philippines, Chanchu killed at least 37 people last weekend and "affected" 53,300 people in wide areas of Luzon and the Visayas, authorities said.