Vietnam is bracing itself for the onslaught of Typhoon Damrey, which has already wreaked havoc on China's island province of Hainan.
Extensive damage has been recorded in Hainan, southern China
More than 100,000 people have left the Vietnamese coast in preparation.
Damrey caused two deaths in Hainan, as well as extensive damage to buildings, infrastructure and crops.
Chinese officials have described it as the worst typhoon to strike the province in decades, with winds comparable to Hurricane Rita.
Two people were killed in Wanning, the coastal city of Hainan where the typhoon made landfall on Sunday, according to China's official Xinhua news agency.
Many homes have been damaged, power lines have been cut, and experts have warned of huge losses to the harvest of rice, rubber and bananas.
About 5,000 people were reportedly left stranded at the airport in the provincial capital, Haikou, after dozens of flights were cancelled.
"The primary threat now is strong winds, but judging from our experience in recent years, river floods are also possible if the heavy rains continue," a disaster relief official told Reuters news agency.
He said more than 170,000 people in the area had been moved to safety.
Areas of nearby Guangdong province have also been evacuated, according to state television.
One fisherman was reported missing there, after three boats capsized in choppy seas, the China Daily said.
According to Xinhua, the typhoon packed winds up to 198 km/h (125mph), making it comparable with the 193km/h (120mph) gusts recorded when Hurricane Rita hit the Texas-Louisiana coastline over the weekend.
Experts say that Damrey will still be generating heavy winds when it makes landfall in Vietnam early on Tuesday morning.
Tens of thousands of Vietnamese are currently preparing to leave coastal districts in Thanh Hoa and Nghe An provinces, while others have been mobilised to reinforce sea dykes.
While still a tropical storm last week, Damrey triggered rains in the Philippines that killed at least 18 people.
Typhoons frequently hit Taiwan, the Philippines, Hong Kong and southern China throughout the summer and autumn.
This is the 18th typhoon to hit China this year.