Unicef trucks filled with emergency water, sanitation and hygiene supplies for thousands of Rohingya children are headed to Cox's Bazar, with a steady stream of supplies in the pipeline for the coming days and weeks.
Up to 400,000 Rohingya have fled Myanmar for Bangladesh since August 25, with thousands more arriving every day, the Unicef said on Thursday.
Around 60 per cent are children, according to preliminary estimates.
The sheer number of refugees has overwhelmed pre-existing refugee camps, with new arrivals seeking shelter anywhere they can find space.
"There are acute shortages of everything, most critically shelter, food and clean water," said Edouard Beigbeder, Unicef's Representative in Bangladesh.
"Conditions on the ground place children at risk of high risk of water-borne disease. We have a monumental task ahead of us to protect these extremely vulnerable children."
Supplies include detergent powder, soap, and pitchers and jugs for containing water, along with nappies, sanitary napkins, towels and sandals.
Unicef is also supporting the Department of Public Health Engineering with water treatment plants and carriers, and is working with partners on the ground to install and rehabilitate tube wells.
These items are part of a first wave of supplies that will massively scale-up Unicef's emergency response to the growing number of Rohingya children in Bangladesh," Beigbeder said.
Unicef has appealed for $US 7.3 million to provide emergency support to Rohingya children over the next four months.