Haze in Thailand's northern Lampang province severely affected aviation in the province on Sunday.

The worst haze in five years has affected seven northern provinces including Lampang, Chiang Rai, Chiang Mai, Lamphun, Nan, Phrae and Phayao with dust particles exceeding safe levels for seven straight days.

Dust particles still blanketing Lampang was measured at about 200 microgrammes per cubic metre (ug/cum) on Saturday, well above safe level of 120 ug/cum for dust particles smaller than 10 microns.

Poor vision forced a Bangkok-Lampang domestic flight to land at central Sukhothai province Sunday morning and to be suspended until it is confirmed of safety by the province's meteorological office.

Visibility in Lampang province was reduced to 10 meters and street lights had to be turned on for almost the entire day to ensure motorists' safety.

Local residents in the affected provinces have been told to avoid outdoor activities or to use face masks when going outside as small dust particles could cause respiratory and other ailments.

Environmental authorities blamed crop burning as the major cause of the haze problem in the northern region.