The sharp increase is the result of more people leaving Myanmar and a more detailed count of those already in Bangladesh, Mohammed Abdiker, director of operations and emergencies for the United Nations migration agency, the International Organization for Migration, said on Twitter.

The refugees in Bangladesh are mostly women and children who have arrived on foot, the United Nations refugee agency said. Some have tried to make dangerous crossings by boat. Last week, at least 46 Rohingya were found dead along the banks of the Naf River, which forms part of the border between Myanmar and Bangladesh.

The Rohingya are a Muslim ethnic group that has faced severe repression in Myanmar, where a Buddhist majority has long ruled. About one million Rohingya live in Rakhine State in the west of the country. An additional 300,000 to 500,000 live in Bangladesh, many of them in grim refugee camps.

Daw Aung San Suu Kyi, the de facto leader of Myanmar and a Nobel Peace Prize laureate for her long struggle against military rule, has come under increasing international criticism for the plight of the Rohingya. Bishop Desmond Tutu of South Africa, also a Nobel laureate, wrote in a letter Thursday that it was “incongruous for a symbol of righteousness to lead such a country” that “is not at peace with itself, that fails to acknowledge and protect the dignity and worth of all its people.”

Senator John McCain of Arizona also wrote to Ms. Aung San Suu Kyi this week, noting that he had been her friend and supporter and calling on her “to take an active role in putting a stop to this worsening humanitarian crisis as it spreads throughout the country.”