Burmese officials have begun the first national census in three decades, but are refusing to allow people to class themselves as Rohingya.
The UN, which is helping to carry out the census, said all Burmese should be allowed to choose their own ethnicity.
But Burmese officials said the Muslim Rohingya must call themselves Bengali or they would not be registered.
The government of Myanmar, also known as Burma, views Rohingyas as immigrants and denies them citizenship.
The Rohingya, on the other hand, feel they are part of Myanmar and claim persecution by the state.
Many Buddhists are hostile towards Rohingyas.
In 2012 hostility erupted into full-scale violence in Rakhine state, and thousands of Rohingyas were forced to flee their homes.
Sporadic violence has continued, and international aid agencies working in Rakhine were attacked last week.
The UN has described the Rohingya as one of the most persecuted minorities in the world.
Correspondents say the census asks detailed questions about religion and ethnicity, raising fears that it could heighten tension.
Rumours that the Rohingya ethnicity would be recognised on the census prompted many Buddhist Rakhines to pledge to boycott the poll.
"If a household wants to identify themselves as 'Rohingya', we will not register it," said government spokesman Ye Htut.