BANGKOK, March 14 (Xinhua) -- Thailand's northern and northeastern parts have been blanketed by haze, leading to cancellations of morning flights between popular destinations until Saturday.

Smog-induced poor visibility has forced Bangkok Airways to cancel its 10 morning flights between Chiang Mai and Mae Hong Son until Saturday.

"Flights during other hours of the day can still operate as usual," the airport explained.

Fine dust reached hazardous levels in many northern and northeastern provinces on Thursday, with PM 2.5 readings at 64 to 199 micrograms per cubic meter of air.

The maximum safe threshold is 50 mcg.

The air quality index in the famed tourist destination Chiang Mai on Thursday reached the dangerous level of 309, the highest in the country, according to the Pollution Control Department.

Unhealthy levels of particulate levels were also detected in the country's central plains.

Deputy Prime Minister Prawit Wongsuwon blamed the air pollution on forest fires, saying officials were trying to convince people not to burn-off.