At least 18 girls have died after a fire swept through the dormitory of a school in northern Thailand.

The fire broke out at about 11pm local time (5pm Irish time) on Sunday and the girls died as they slept in the private Pitakiatwittaya School Christian primary school in Thailand's northern Chiang Rai province.

Five of their classmates were injured - two of them seriously - and two are still missing, Police Colonel Prayad Singsin, Commander of Vingpatao district in Chiang Rai, said.

The province's deputy governor Arkom Sukapan told AFP: "There were 38 students inside the dormitory when the fire broke out.

"Some were not yet asleep so they escaped.

"But others were asleep and could not escape, resulting in the large number of casualties."

The school belongs to a local foundation and is home to girls aged between five and 12.

It is understood that many of the pupils are from impoverished hill tribes in the mountainous region.

Mr Singsin said the fire had been extinguished but its cause was still being investigated, with forensic officers due to arrive later.