The plant's closure had prompted domestic distributors to aggressively seek oil products in the spot market due to reduced term supplies from the refinery.

"The plant has been running with 90 percent of crude oil input from the Bach Ho grade," Nguyen Hoai Giang, chief executive officer of Binh Son Refining and Petrochemical Co (BSR) said on Monday.

He added that the 130,500 barrels-per-day refinery, which restarted on Saturday after being shut on May 16, could continue crude imports in the second half of the year.

The operator has said the facility was closed so equipment could be checked, with its builder, French oil services group Technip, signing off on the process.

BSR had planned to restart the refinery, which supplies around a third of Vietnam's domestic fuel consumption, by the end of June, but the checks took longer than expected, Giang has said.

The plant's owner in March was looking to sell a 49 percent stake to foreign investors to raise funds and boost its capacity by more than half.

Dung Quat needs over $2 billion of investment to expand its processing capacity by about a third to 192,000 barrels per day (bpd), or 9.5 million metric tons (10.5 million tons) per year.