DHAKA: Five men have been arrested after three children were beaten to death at a juvenile detention centre in Bangladesh, police said Sunday, the latest case to shed light on the treatment of minors in such institutions.

Eighteen boys allegedly had their mouths stuffed with towels and beaten with steel pipes, sticks and cricket stumps after attacking and breaking the hand of a guard at the facility, a police spokesman told AFP.

"Eighteen children were beaten for an hour around noon by the officials and several other children," police inspector Mohammad Rokibuzzaman said on Thursday.

"The injured were initially given first aid. But when one of them was brought dead to a hospital at 6:30pm, the hospital alerted us. Then two more... died," he said.

The bodies of the three boys showed signs of torture and beatings, Rokibuzzaman said, adding they were hit to "teach them a lesson".

Two others remained in a critical condition, he said. Their ages were not released.

The five -- the centre's head, two teachers and a counsellor -- were detained late Saturday amid an ongoing investigation, police said. Eight children were also being held for taking part in the beatings.

About 280 boys are institutionalised at the Children Development Centre in the western city of Jessore. They were either convicted or awaiting prosecution for crimes from minor thefts to rapes and murders.

"The sirs (centre staff) and other children inmates beat us with steel pipes and wood sticks as if we were dogs," one of the other boys who was beaten, Jabed Hossain, told the Bangla Tribune.

"When we passed out, some of us were left under a tree and others sent to their rooms. When we regained consciousness, we were beaten again."

Bangladesh has three such "rehabilitation" facilities -- two for boys and one for girls.

But Abdus Shahid, the head of child rights' group Bangladesh Shishu Odhikar Forum, told AFP the children were "barely developed or corrected there".

"Instead many of them face physical and sexual abuse."

In 2015, the government suspended the head of another centre after 20 boys slashed their wrists during a protest after they were allegedly tortured by a staff member.

"Independent mechanisms to monitor child detention centres should be established so that these children don't face such appalling tragedy," rights activist Rezaur Rahman Lenin told AFP.