The typhoon, packing winds of 200km per hour, pummelled Hainan on Monday, uprooting trees, flooding roads and causing an island-wide power blackout.
The Civil Affairs Ministry said that as of Monday night the storm had caused nearly 8.5 billion yuan ($1.05 billion) in damage in Hainan, Guangdong and Guangxi provinces, while 436,000 people had been evacuated.
By Tuesday, the typhoon had slammed ashore in Vietnam, breaching a network of sea dikes and forcing the evacuation of nearly 300,000 people along the coastal region.
Hainan Vice Governor Wu Changyuan said that 20,000 homes had been flattened on the island province, while 380km of roads had been damaged and 704,000 hectares of cropland ruined, Xinhua news agency said.
By Tuesday evening, Xinhua put economic losses at 10 billion yuan and the death toll at 16.
Extensive damage to Hainan's electrical grid would also require costly repairs, while the island's oil industry was facing damage to facilities and potential cutbacks in production, press reports said.
A ship was blown ashore in China
by the typhoon's powerful winds
Damrey, the most powerful typhoon to hit northern Vietnam in a decade, injured nine people after it landed in Thanh Hoa province early on Tuesday, packing winds of up to 102km per hour, said Le Van Thao of the National Meteorology Centre.
Thanh Hoa is 160km south of Hanoi.
About 144,000 people from Thanh Hoa and another 145,000 from three surrounding provinces were evacuated from low-lying homes, schools and local government buildings before the storm hit, said provincial disaster official Tran Quang Trung.
National broadcaster VTV reported that five people were injured by falling power poles in Thanh Hoa, while disaster officials said four workers had been slightly injured as they cleared downed trees from the streets.
About 700 people were stranded in Quang Cu village in Thanh Hoa after surging waters breached the sea dike and engulfed their homes, VTV reported. Border guards have been dispatched to help them.
Initial damage is estimated at $5.2 million in Thanh Hoa alone, disaster relief officials said. Some 950 homes were completely destroyed while another 9000 had their roofs blown off.
A power blackout was reported in Thai Binh and Thanh Hoa provinces, home to five million people.
More than 25,000 soldiers have been sent to help reinforce sea dikes and evacuate people, state media reported.