Dozens of Rohingya villages now lie empty after their residents fled violence in Rakhine state, according to Burma's government. One hundred and seventy-six of 471 villages were abandoned, spokesman Zaw Htay said.
Amarpreet Singh, managing director of Khalsa Aid India, told The Indian Express: "We had come prepared for providing relief to some 50,000 people, but there are more than three lakh [300,000] refugees here. They are living without water, food, clothes and shelter. They are sitting wherever they can find a corner."
Refugee camps had become overcrowded, he added.
Rohingya Muslims face widespread persecution in Buddhist-majority Burma, where the recent violence has driven hundreds of thousands to seek refuge overseas.
Zaw Htay did not use the name Rohingya. Members of the ethnic group are commonly referred to as "Bengalis" by many in Burma who insist they migrated illegally from Bangladesh.
He also said Burma would not allow all people who fled to return. He said: "We have to verify them. We can only accept them after they are verified."
The government blames the Rohingya for the violence, but journalists who visited the region found evidence that raises doubts about its claims that Rohingya set fire to their own homes.
Many of the Rohingya who flooded into refugee camps in Bangladesh told of Burmese soldiers shooting indiscriminately, burning their homes and warning them to leave or die. Others said they were attacked by Buddhist mobs.