Bangladesh on Wednesday defended the use of barbed-wire fences around vast camps holding almost a million Rohingya refugees, after a major fire left at least 15 people dead and nearly 50,000 homeless.

The fire, which gutted some 10,000 refugee shanties, was the deadliest since more than 740,000 Rohingya fled a military crackdown in Myanmar in 2017 that United Nations investigators concluded was executed with "genocidal intent".

The U.N., aid groups and Rohingya leaders said that the fences erected by the military hampered rescue work and caused injuries during Monday's 12-hour blaze in the maze of bamboo-and-tarp huts.

"Rescue efforts proved to be challenging as a result of the presence of perimeter fencing," a joint statement from the U.N., local and international aid agencies said, "In some instances, refugees themselves cut through the fence to escape the fire," it said.

Bangladesh's refugee commissioner Shah Rezwan Hayat defended the fences, which were built in recent months amid a worsening law and order situation in the vast settlements, "I don't believe these fences have hampered rescue efforts," he said.

"There were enough roads in the camps and hundreds of our officials, policemen and volunteers were there to rescue them," he told Agence France-Presse (AFP). He said the fences were not built inside the camps and were there to act as barriers between blocks of shanties.

"The barbed-wire fences were erected on the outer boundary of the camps to ensure the safety and security of the Rohingya people. If the fencing acted as a barrier, how could dozens of fire fighting vehicles, police vans enter the camps within 20 minutes after the fire?" he said.

Earlier Rohingya refugees vented their anger to reporters and on social media saying some were injured as they were trying to flee the fire through the fences. Hayat also rejected the U.N.'s claim that some 400 people were still missing after the fire, saying most refugees have taken shelter with relatives in neighboring camps, in schools and refugee transit centers.

"We are on the ground. So far we don't think anybody is missing," he said, adding that the authorities and the U.N. agencies were now building tents and temporary shelters and most refugees have started returning.

A police spokesperson said the local police station did not receive any reports of missing people from the Rohingya. He said officers were questioning eight people over the fire. Hayat said preliminary findings suggested the fire originated from a stove in a shelter and then quickly spread due to strong wind and cooking gas cylinders. A full investigation is continuing, he said.