SHANGHAI (AFP) - China announced on Sunday its highest alert for Typhoon Haiyan as six crew members of a cargo boat were reported missing.

The China Meteorological Administration hoisted the "red" signal, the highest in its four-tier warning system, as the typhoon brushed the southern island province of Hainan.

Six people were lost at sea after the mooring rope of their vessel was cut in the storm, causing the ship to drift, the official Xinhua news agency said.

The storm brought heavy rains and cancelled flights in Hainan, after devastating the Philippines as a super typhoon.

In Hainan's Sanya city, a major tourist resort, more than 13,000 people were evacuated and over 400 boats called back to port, state media said.

More than 200 flights at Hainan's two airports, in Sanya and Haikou, were cancelled or delayed, reports said.

The Meteorological Administration is forecasting the typhoon will move towards China's southern region of Guangxi.

The United States Navy's Joint Typhoon Warning Centre predicts Haiyan will make landfall in Vietnam before crossing the border into China.

Vietnam has evacuated more than 600,000 people ahead of the typhoon's expected arrival on Monday morning, the authorities there said.

In the Philippines, the death toll from the typhoon that decimated entire towns could soar well over 10,000, officials warned.