At least 15 people have been killed and another 400 are missing after a huge fire at a Rohingya refugee camp in Bangladesh.
"It is massive, it is devastating," said UNHCR's Johannes Van der Klaauw, who joined a briefing in Geneva online from the Bangladeshi capital of Dhaka.
"We still have 400 people unaccounted for, maybe somewhere in the rubble," he said.
He said the UNHCR had reports of more than 550 people injured and about 45,000 displaced.
Bangladeshi officials are investigating the cause of the blaze as officials, aid workers and families sift the debris looking for further victims.
The fire ripped through the Balukhali camp near the south-east town of Cox's Bazar late on Monday, burning through thousands of shanties as people scrambled to save their meagre possessions.
"Everything has gone. Thousands are without homes," Aman Ullah, a Rohingya refugee from the Balukhali camp, told Reuters.
"The fire was brought under control after six hours but some parts of the camp could be seen smoking all night long."
Police have so far confirmed seven deaths.
"The cause of the fire is still unknown" and authorities are investigating the matter, Zakir Hossain Khan, a senior police official told Reuters.
Sanjeev Kafley, the head of International Federation of Red Cross and Red Crescent Societies' delegation in Bangladesh, said more than 17,000 shelters had been destroyed and tens of thousands of people displaced.
More than a thousand Red Cross staff and volunteers worked with fire services to extinguish the blaze, spread over four sections of the camp containing roughly 124,000 people, he said. That represents about 10 per cent of an estimated one million Rohingya refugees in the area, Mr Kafley said.
"I have been in Cox's Bazar for three-and-a-half years and have never seen such a fire," he said.
"These people have been displaced two times. For many, there is nothing left."
Barbed wire
Some witnesses said many people got trapped because of the barbed-wire fencing around the camp, leading international humanitarian agencies to call for its removal.
Humanitarian organisation Refugees International, which estimated 50,000 people had been displaced, said the extent of the damage might not be known for some time.
"Many children are missing, and some were unable to flee because of barbed-wire set up in the camps," it said.
John Quinley of Fortify Rights, a rights organisation working with Rohingya, said he had heard similar reports. The fences, he said, had hampered the distribution of humanitarian aid and vital services at the camps in the past.
"The government must remove the fences and protect refugees," Mr Quinley said.
"There have now been a number of large fires in the camps including a large fire in January this year... The authorities must do a proper investigation into the cause of the fires."
The vast majority of the people in the camps fled Myanmar in 2017 amid a military-led crackdown on the Rohingya that UN investigators said was executed with "genocidal intent", charges Myanmar denies.
