As the victims of Thursday's religious school fire were buried yesterday, calls were mounting for the government to strengthen regulation of such schools, which are often not registered.

Twenty-one young students and two wardens trapped behind barred windows were killed in the pre-dawn blaze that swept the top floor of the school building in Kuala Lumpur. The school, Darul Quran Ittifaqiyah Tahfiz, did not have an occupancy permit from the Fire and Rescue Department even though it has been operating for a year.

While there have been 31 fires involving such religious schools this year, officials said the one at Darul Ittifaqiyah Tahfiz is the worst in 20 years. Tahfiz schools come under the purview of the Islamic Development Department rather than the Education Ministry.

Prime Minister Najib Razak, who visited the school site with several ministers last night, earlier reminded the management of tahfiz schools to adhere strictly to all safety regulations.

The government will set up a task force to investigate the fire, Deputy Prime Minister Ahmad Zahid Hamidi said on Thursday.

The incident stunned and outraged Malaysians as many of the victims were young boys.

"You can't just blame it all on fate. It could have been avoided if there was enforcement. I don't agree with the minister who said the government was not likely to take action against the school," said a resident who gave her name only as Sharifah.

"The bottom line is, 23 people are dead, so someone should be held responsible," the 46-year-old added.

Urban Wellbeing, Housing and Local Government Minister Noh Omar had said on Thursday that no action would be taken against the school as it had "suffered enough".

According to the Fire and Rescue Department, there were 211 fires at tahfiz schools nationwide between 2015 and this year.

Dr Siti Hasmah Mohamad Ali, the wife of former prime minister Mahathir Mohamad, said the fire was not the result of "fate" but of human error. Those who manage the school should also take responsibility for the children's well-being, she added.

"These children were sent to the school to learn about their religion… I am sad because this tragedy could have been avoided," she said.

Meanwhile, Malaysian Muslim Consumers Association chairman Nadzim Johan said a group of 10 people had been spotted loitering "suspiciously" in front of the school on Wednesday night. He said they were captured on close-circuit television cameras at the association's office, which is located next to the school. "We will share the footage with the police," he added.

National police chief Mohamad Fuzi Harun yesterday confirmed a man has been called in to facilitate investigations into the fire.

The Fire and Rescue Department had said there was a possibility that the blaze was an act of mischief.

But Minister in the Prime Minister's Department Jamil Khir Baharom said there was no reason to suspect foul play.