South Korean's BS Shipping has increased a product tanker newbuilding series in Vietnam.
Pha Rung Shipyard said four 6,500-dwt ships will be delivered at three-month intervals from 2018.
TradeWinds reported the original deal for two vessels in 2016.
The Toan Viet website cited Pha Rung general director Vu Huu Chien as saying the first vessel, YN Yeosu, has been launched this month and will be delivered in the first quarter.
