At least 10 children and four women were killed when a boat carrying Rohingya fleeing violence in Myanmar capsized off Bangladesh on Thursday, as the number of new arrivals topped 500,000.

The latest disaster came as a UN visit to Myanmar's conflict-battered Rakhine state was postponed Thursday, thwarting efforts to reach the epicentre of violence for the first time since the start of the massive Rohingya exodus.

At the scene of the accident, witnesses and survivors said the boat overturned just yards from the coast after apparently hitting a submerged object and was later washed ashore in two parts along with the victims' bodies.

"They drowned before our eyes," said Mohammad Sohel, a local shopkeeper.

"Minutes later, the waves washed the bodies to the beach."

One distraught survivor said he had set off for Bangladesh from a coastal village in Myanmar late Wednesday with his wife, who was killed in the disaster along with one of his children.

"The boat hit something underground as it came close to the beach. Then it overturned," Nurus Salam told AFP.

Another survivor who was seen weeping on the beach told an AFP reporter at the scene that her parents and children were missing.

Local police constable Fazlul Karim told AFP 14 bodies had so far been washed ashore, and there were fears the number could rise.

The UN said more than half a million refugees had now crossed into Bangladesh from Myanmar since August 25, when attacks by Rohingya militants on security posts prompted a military crackdown.

It said the flow of new arrivals had slowed and the new figure of 501,800 -- up from around 480,000 -- was due mainly to the counting of refugees not previously included in the tally.

- UN visit postponed -

The huge influx of Rohingya to Bangladesh -- the largest mass movement of refugees in the region in decades -- has created a humanitarian crisis as the government and aid agencies struggle to provide food, clean water and shelter.

Those who have made it to Bangladesh have brought with them multiple accounts of murder and systematic arson of their villages by Myanmar soldiers and mobs of ethnic Rakhine, who are Buddhists.

Rakhine has long been a cauldron of ethnic and religious tensions, but the last five years has seen communal relations plunge to their worst yet, and there are reports thousands more Rohingya could be waiting to enter Bangladesh.

Images circulated by Myanmar authorities on Wednesday showed hundreds waiting to cross the Naf River that divides the two countries.

Access to Rakhine by relief agencies and global media has been heavily controlled by Myanmar's army and government, making it difficult to assess the situation there.

On Thursday, the UN said a planned visit to the state was postponed due to weather conditions there.

The United Nations has been demanding access since its humanitarian organizations were forced to pull out of Rakhine when Myanmar's military launched operations against Rohingya rebels in late August.

Police in Bangladesh say an estimated 120 Rohingya have drowned trying to reach the country's shores in small fishing boats that coastguards say are woefully inadequate for the rough seas, many of them children unable to swim.

Survivors said the boat that capsized on Thursday was carrying around 40 people, many of them children.

Local police chief Abul Khair said at least 18 people survived the accident and they were trying to find out how many were missing.

"We have sent nine of the survivors to hospitals," he told AFP.

Source: AFP