The children, all boys, died of suffocation in the fire at a dormitory of a school next to a mosque in Yangon at about 2:40 a.m., neighbours and officials said.
"A total of 13 boys were killed in the fire caused by overheating of a transformer. They died of suffocation after inhaling too much smoke," a Central Fire Service duty officer said.
The fire could raise tensions following Buddhist-led mob violence against Muslims elsewhere in the country, including firebombings of mosques and Muslim homes. Since 43 people were killed in violence that erupted in
Meikhtila town on March 20, unrest has spread to at least 15 other towns and villages.
Neighbours and witnesses said it appeared the crowded Yangon dormitory locked its doors due to heightened security concerns.
"It seemed the boys didn't get a chance to get away because the doors were locked because of the unstable situation," a resident said.
According to official records, electrical faults and overheating are major causes of fires in Yangon.