The Vietnamese navy searched for six fishermen near the Paracels archipelago, and thousands of people were evacuated in the north of the country on Sunday due to threats of flash floods and landslides.
Typhoon Conson, which killed 39 in the Philippines and two in China, was downgraded to a tropical storm as it hit northern Vietnam late on Saturday.
In Vietnam, a person drowned while swimming in the northern province of Thanh Hoa and 11 people, including the six fishermen, were missing, the government said on Sunday.
A child also drowned when a barge capsized in the northern province of Quang Ninh, a local newspaper said in an online report (www.baoquangninh.com.vn).
Three naval ships arrived in an area near the Paracels in the South China Sea on Saturday night to search for the six fishermen after their boat sank while seeking shelter, state-run Voice of Vietnam radio said.
It said the army had also sent 3,500 soldiers to help evacuate people in coastal provinces and others will be moved from dangerous areas in four mountainous provinces due to the threat of flooding.
The region lies far from Vietnam's Mekong Delta food basket in the south, which supplies 90 per cent of rice for exports.
Vietnam Airlines said it would resume operations on Sunday and planned extra flights to help passengers from the 10 flights it cancelled on Saturday.
Typhoons and tropical storms regularly hit the Philippines, China, Taiwan, Japan and Vietnam in the second half of the year, gathering strength from the warm waters of the Pacific Ocean or South China Sea before normally weakening over land.