Geneva: The U.N. refugee agency urged Bangladesh on Tuesday to speed up vetting of up to 15,000 Rohingya refugees "stranded" near the border after crossing into the country from Myanmar and move them further inland to safer and better conditions.

Some 582,000 Rohingya are now known to have fled since violence erupted on Aug. 25 in northern Rakhine state, where they lack access to food and health care, U.N. officials said.

"We are gravely concerned about humanitarian conditions in Bangladesh, where thousands of new arrivals are stranded near the border," UNHCR spokesman Andrej Mahecic told a Geneva news briefing.

An estimated 10,000 to 15,000 have entered Bangladesh through the Anjuman Para border crossing point since Sunday night, many of whom described walking for about a week to reach the border, he said.

"We are advocating with the Bangladesh authorities to urgently admit these refugees fleeing violence and increasingly difficult conditions back home. Every minute counts given the fragile condition they are arriving in," Mahecic said.

The delay was due to screening by Bangladesh border guards, he said, emphasising this was the right of any government.

U.N. aid agencies have not had access to the shrinking Rohingya population in northern Rakhine state since the Aug. 25 coordinated insurgent attacks on police posts and army campaign which the U.N. rights office has likened to "ethnic cleansing".

Jens Laerke, spokesman of the U.N. Office for the Coordination of Humanitarian Affairs (OCHA), said that Rohingya in Rakhine now faced a "desperate choice whether to stay or go", not only due to the violence but also humanitarian needs.

"The lack of food, lack of health care and so on. So that is certainly a factor that is strongly in play as of now," he said.

Nearly 60 per cent of the 582,000 refugees who have fled Myanmar since August 25 are children – and thousands more are crossing each week, UNICEF spokeswoman Marixie Mercado said.

UNICEF, which is providing clean water every day to 40,000 people in Cox's Bazar, Bangladesh, and has installed thousands of toilets, may have to stop operations by the end of November unless further funds are received, she said.

A UN inter-agency appeal of $434 million for Rohingya in Bangladesh and host communities is only 24 percent funded, OCHA's Laerke said.