Videos posted on Twitter showed the three-story building was engulfed in raging fire before the fire fighters arrived, Xinhua reported. According to witnesses, they called for help through the gridlock windows.
Fire-fighters had the blaze out within an hour, but the damage was extensive.
"They were sent to the Kuala Lumpur Hospital for treatment", he said.
A fire accident took place at Darul Quran Ittifaqiyah, a "tahfiz" boarding school.
These schools are unregulated by the education ministry and fall under the purview of the religious department.
"The forensic team is doing the laboratory tests".
The Malaysian government is covering the funeral costs of the victims, reports The Star Online.
Prime Minister Najib Razak offered his condolences via Twitter.
Casualties in a Fire at a Religious School in Kuala Lumpur
"It is one of the nation's most exceedingly terrible fire catastrophes in the previous 20 years", Khirudin Drahman, executive of the fire and protect office, told AFP. "May their souls be blessed by Allah".
Photo The authorities investigating a deadly fire at an Islamic religious school in Kuala Lumpur, Malaysia, on Thursday.
"The building was encompassed by metal barbecues that couldn't be opened from within". "I thought there were people fighting", the 46-year-old said.
"My friend climbed through the window and passed me the baby as I waited on the second floor", he added. Only inside did the intensity of the inferno become clear. Once inside, emergency officials described blackened rooms, charred bed frames lining the walls and burned bodies huddled in corners.
School principal Mohamad Zahid Mahmod has told local media the students were being housed in a temporary building because of renovation work at the main school building.
This religious school was operating without a license, said the minister of Territories.
"He was in a jovial mood - he loved studying here", he said, adding another of his sons had been "saved" as he had refused to attend the school for the past fortnight. More than 200 fires are said to have been recorded nationwide at private religious schools since 2015.
There are 519 tahfiz (Qur'an memorization) schools registered in Malaysia.
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