However it changed course, returned to sea and gathered strength before heading for Vietnam.
More than 3,000 passengers were stranded in Hainan as ferries linking the island province with the Chinese mainland were suspended.
Children and elderly people were moved to higher ground in Vietnam as part of a government plan to evacuate more than 400,000 people before Lekima hits the central coast.
An area stretching more than 300km between the provinces of Thanh Hoa and Quang Binh faced "extreme danger" and people would have to be evacuated, according to a government report.
The national weather centre has said that the storm would arrive on Wednesday and Lekima would later weaken into a depression as it moved inland to the northwest.
The government also warned of landslides and flash floods in the central provinces.
The storm, which killed five people in the Philippines last week, is not expected to disrupt the production of coffee, rice and crude oil, Vietnam's key export products.
Vietnam is hit by up to 10 storms a year and Lekima is the fifth in 2007.