A Rohingya Muslims girl rests on a pile of bags, as she waits with others to walk towards a camp for refugees after crossing into Bangladesh from Myanmar, in Teknaf, Bangladesh, Friday, Sept. 29, 2017. More than a month after Myanmar's refugees began spilling across the border, the U.N. says more than half a million have arrived. The prejudice and hostility that Rohingya Muslims face in Myanmar stretch beyond the country's notoriously brutal security forces to a general population receptive to an often-virulent form of Buddhist nationalism that has seen a resurgence since the end of military rule. (AP Photo/Gemunu Amarasinghe)
A Rohingya Muslims girl rests on a pile of bags, as she waits with others to walk towards a camp for refugees after crossing into Bangladesh from Myanmar, in Teknaf, Bangladesh, Friday, Sept. 29, 2017. More than a month after Myanmar's refugees began spilling across the border, the U.N. says more than half a million have arrived. The prejudice and hostility that Rohingya Muslims face in Myanmar stretch beyond the country's notoriously brutal security forces to a general population receptive to an often-virulent form of Buddhist nationalism that has seen a resurgence since the end of military rule. (AP Photo/Gemunu Amarasinghe) Credit: Gemunu Amarasinghe

Teknaf, Bangladesh — He trekked to Bangladesh as part of an exodus of a half million people from Myanmar, the largest refugee crisis to hit Asia in decades. But after climbing out of a boat on a creek on Friday, Mohamed Rafiq could go no further.

He collapsed onto a muddy spit of land cradling his wife in his lap — a limp figure so exhausted and so hungry she could no longer walk or even raise her wrists.

The couple had no food, no money, no idea what to do next. Their two traumatized children huddled close beside them, unsure what to make of the country they had arrived in just hours earlier, in the middle of the night.

Rafiq said their third child, an 8-month-old boy, had been left behind. Buddhist mobs in Myanmar burned the child to death, he said, after setting their village ablaze while security forces stood idly by — part of a systematic purge of ethnic Rohingya Muslims from Buddhist-majority Myanmar that the United Nations has condemned as “a textbook example of ethnic cleansing.”

Five weeks after the mass exodus began on Aug. 25, the U.N. says the total number of arrivals in Bangladesh has now topped 501,000.

The crisis began when a Rohingya insurgent group launched attacks with rifles and machetes on a series of security posts in Myanmar on Aug. 25, prompting the military to launch a brutal round of “clearance operations” in response. Those fleeing have described indiscriminate attacks by security forces and Buddhist mobs, including monks, as well as killings and rapes.

On Friday, dramatic scenes played out over and over as hordes of Rohingya who had crossed into Bangladesh overnight tried to make their way further inland. They trudged out of boats and through mud that in some places was knee deep. Men carried babies and old women on their backs. Everyone was exhausted.

Myanmar’s government, led by Nobel Peace Prize winner Aung San Suu Kyi, does not allow independent media free access to northern Rakhine state, from where the Rohingya are fleeing. While fires are no longer visible from the Bangladeshi border, some refugees told The Associated Press that their homes had been burned as recently as two days ago.

Rafiq said he and his wife, Noor Khatum, fled their home in the Maungdaw village in Khai Dar Para in the first week of September, after police and soldiers moved in and Buddhist mobs, including monks, set fire to homes there in the middle of the night.

Rafiq managed to get his 5-year-old daughter out, while his wife carried their 2-year-old son. But their house, made of wood and sticks, burned quickly, collapsing on their baby boy before they could save him.

After fleeing, they took shelter with relatives in another village, but several days later that village, too, was torched by Buddhist mobs. Rafiq and his family then hid with others in an abandoned house near the border for two weeks, but had no money to pay boatmen to take them across the Naf River to Bangladesh.

So for two days, Rafiq helped other families escape, carrying them and their goods in exchange for amounts of cash. On Friday at 3 a.m., his own family finally made it out.

Now, in Bangladesh, a far more uncertain chapter of their lives has begun.

“We don’t know where we will go,” Rafiq said forlornly, as a long line of families trudged single file toward the town of Teknaf, where authorities were assessing the new arrivals and trucking them to camps further north. “We have nothing. We don’t know what we will do.”