Citing 'unhealthy air', Vietnam tells people to limit outdoor activities

People wear protective masks while riding on a street in Hanoi, Vietnam May 21, 2018. Picture taken May 21, 2018. REUTERS/Kham

HANOI (Reuters) - Vietnam warned its people on Tuesday to limit outdoor activities because the air quality in the Southeast Asian country has persistently been at "unhealthy" levels for days.

The levels of hazardous small particles known as PM2.5 in the air at the country's two largest cities, Hanoi and Ho Chi Minh City, have been rising persistently since early last month, exceeding "Vietnamese standards", the government said in a statement.