The 200,000-barrel-per-day Nghi Son Refinery and Petrochemical has a leak at the RFCC unit, the government said in a statement.
Reuters first reported on the shutdown late last month.
The Ministry of Industry and Trade has asked fuel traders to increase their imports to compensate for the shortfall "to ensure sufficient fuels for the local market until the end of the first quarter," the government said.
Nghi Son refinery is 35.1% owned by Japan's Idemitsu Kosan Co, 35.1% by Kuwait Petroleum, 25.1% by Vietnam's state oil firm PetroVietnam and 4.7% by Mitsui Chemicals Inc.
(Reporting by Khanh Vu; editing by Barbara Lewis)