Mun was around 500 kilometers (310 miles) from the major port city Hai Phong and Quang Ninh Province, home of the famous Ha Long Bay, at 7 p.m. Tuesday.

The storm will continue moving northwest at 10 kilometers per hour and growing stronger as it comes close to Vietnam's northern coast on Thursday morning, said the National Center for Hydro-Meteorological Forecasting.

Rough waters are forecast to hit the Gulf of Tonkin, including tourist islands Bach Long Vi, Co To and Cat Hai, from Wednesday afternoon.

The northern and north central regions of Vietnam, including the capital city of Hanoi, will suffer heavy rains and thunderstorms until Friday.

Flooding could appear at rivers and streams in the north and central regions, and flashfloods and landslide should be expected, Vietnam's weather forecast agency said.

Mun already claimed damage when it was a tropical depression on Monday afternoon. Sea waves of over two meters high hit a vessel carrying 50,000 liters of diesel off Binh Thuan Province in the south central coast.

Local officials are rushing to remove the oil from the ship and preparing to deal with possible oil spills.