Doan Van Tan, director of the Urban Transport Management and Operation Center, said the installation would start next month and take six months to complete.

The system would be capable of automatically detecting and putting out fires by spraying high-pressure fog, he said.

Firefighting and rescue drills are carried out regularly in the tunnel to be prepared for possible incidents.

The Thu Thiem tunnel, built in 2011, is the only river tunnel in Vietnam and the largest of its kind in Southeast Asia.

It is 1.49 kilometers long, 33 meters wide and nine meters high and has six lanes and two emergency exit lanes.

Some 47,000 cars and up to 270,000 motorbikes use the tunnel every day.