Police in Burma opened fire at hundreds of protesters angry about a ban on a local festival, killing seven people, officials have said.

The protesters in Rakhine state marched through the ancient city of Mrauk-U and ransacked a government building on Tuesday after authorities banned the anniversary celebration of the founding of the old kingdom, saying they were not informed about it beforehand.

Deputy director of the regional government Tin Maung Swe said police warned the mob to stop but they were being physically attacked and officers had to respond after initially using rubber bullets.

The protest involved Rakhine Buddhists.

Rakhine is also home to minority Rohingya Muslims, who have long faced persecution that has seen about 650,000 people driven away from their homes into Bangladesh since August.

The UN office in Burma said it was concerned by reports of violent clashes and urged respect for the rights to peaceful assembly and freedom of expression.

It also called on security forces and demonstrators to act with restraint and avoid further violence, and for authorities to investigate any disproportionate use of force.