As of 7 a.m. on Wednesday the storm lay centered 480 km east-northeast of Southwest Cay Islet in Vietnam's Spratly Islands with wind speeds of up to 115 kph, according to the National Center for Hydro-Meteorological Forecasting.

In the next 24 hours it is expected to move west-northwest at around 15 kph, centered 400 km to the north of Southwest Cay with winds of 90 kph on Thursday morning.

In the next 48 hours the storm, the seventh to affect Vietnam this year, will turn south-southwest at 10-15 kph and weaken into a tropical depression.

By 7 a.m. on Friday its eye is expected to move to 160 km north-northwest of Southwest Cay, and the maximum wind speed will be down to 60 kph.

Rough seas can be expected for the next few days in the northern and middle regions of the East Sea.

As of 6 a.m. on Wednesday 11 fishing vessels were still in the storm’s vicinity, the Vietnam Border Defence Force and the Directorate of Fisheries said.

Authorities are trying to warn them about the storm and guide them to safety.

Storm Kammuri, known in the Philippines as Tisoy, has killed at least three people there, disrupted air travel and forced government offices and schools to shut when it hit on Tuesday.

Authorities had to evacuate 225,000 people before its arrival.

The powerful typhoon forced organizers of the 30th SEA Games to reschedule about half of the events set for Tuesday.

At least 16 water-based and outdoor events, including beach volleyball, surfing and sailing, had to be postponed. But organizers said the competition would finish on time, on December 11.

Vietnam is hit by up to 10 tropical storms every year. There were nine last year.