At least seven people were killed and 12 injured after the police in Myanmar’s Rakhine state opened fire on Buddhist demonstrators on Tuesday, Reuters reported.

The demonstrators had gathered in Mrauk U late on Tuesday to protest against a ban on an annual celebration of the fall of the ancient Arakan kingdom, BBC reported. Mrauk U is the historic capital of the ancient kingdom. This year, the authorities had denied permission for the event, the report said.

Around 4,000 people surrounded a government building after taking part in the annual ceremony, the secretary of the Rakhine state government, Tin Maung Swe, told Reuters. Swe said the police first used rubber bullets and resorted to shooting after the the crowd refused to leave. “The conflict happened when some people tried to seize guns from the police,” he added.

The United Nations has asked authorities to “investigate any disproportionate use of force or other illegal actions that may have occurred in relation to this incident”.

While several ethnic groups have been demanding autonomy since the country’s independence from Britain in 1947, tensions in Rakhine have risen especially after a Myanmar Army operation in August 2017 triggered communal tension and resulted in more than 6,50,000 Rohingya Muslims fleeing to Bangladesh.

Myanmar leader Aung San Suu Kyi has faced severe criticism globally for her response to the alleged persecution of Rohingya Muslims in her country.