Myanmar police shot dead seven demonstrators, while 12 were injured in troubled Rakhine State, after a local gathering celebrating an ancient Buddhist Arakan kingdom turned violent.

The demonstrators gathered late on Tuesday in Mrauk U township in the northern part of Rakhine to mark the end of the Arakan kingdom, the secretary of the Rakhine state government, Tin Maung Swe, told Reuters.

The violent demonstration underscores the challenges facing Myanmar leader Aung San Suu Kyi in a country where dozens of ethnic groups have been clamouring for autonomy since independence from Britain in 1947.

Some 4,000 people surrounded a government building after the annual ceremony marking the demise of the Arakan kingdom over 200 years ago, Tin Maung Swe said. Organisers did not seek approval from local authorities for the gathering, he said.

“The police used rubber bullets initially but the crowd didn't leave. Finally the security members had to shoot. The conflict happened when some people tried to seize guns from the police,” he said.

Tun Ther Sein, regional MP from Mrauk U, said some of the critically injured protesters were taken to the state capital of Sittwe, a three-hour drive south of the ancient town studded with Buddhist temples.

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

“We urge respect for the rights to peaceful assembly and freedom of expression, and call for the security forces and demonstrators to act with restraint and to avoid further violence,” the agency wrote in a statement.

The US embassy in a statement expressed “deep concern for all innocent people affected by the violence” and hoped “reason and restraint will prevail.”

Myanmar government spokesman Zaw Htay did not respond to requests for comment.

The Rakhine, also known as Arakanese, are one of the 135 officially recognised ethnic groups in Myanmar. Their identity is closely connected to the once powerful Arakanese kingdom along the Bay of Bengal, which was conquered by the Burmese kingdom in 1784. The kingdom was once an important stop on the old silk trade route.

Hope in Bangladesh’s Rohingya camps Show all 15 1 /15 Hope in Bangladesh’s Rohingya camps Hope in Bangladesh’s Rohingya camps Badiul Alam, 52, appointed as the manager of one grouping of refugees, shows the rifle-butt injury he sustained during his flight from Myanmar Hope in Bangladesh’s Rohingya camps Abdur Rahim, 50, fled Myanmar with his family of seven. It took a month for them to walk to Bangladesh, carrying all their possessions on their shoulders. They haven’t yet found a place to put down their belongings after a gruelling journey Hope in Bangladesh’s Rohingya camps Various refugee camps – Kutupalong, Balukhali and Moinerghona – have merged into one vast sprawl spread over many muddy hills that just a few months ago were a rolling green nature reserve Hope in Bangladesh’s Rohingya camps A Red Cross aid-worker supervises an aid distribution point on the edge of the Moinerghona camp, saying they have never known refugees anywhere in the world stand so patiently in line in such heat to be registered and receive aid without any tension or anger Hope in Bangladesh’s Rohingya camps Last week the governments of Bangladesh and Myanmar signed a deal to return the Rohingya to Rakhine. But many worry that they will face further reprisals if they return, and there was no mention of what would happen to those who refused to go back Hope in Bangladesh’s Rohingya camps A quiet calm pervades the camps. Is it relief at being free from fear, or do feelings about the horrors witnessed remain suppressed? Hope in Bangladesh’s Rohingya camps The aid response is focused on providing food, water and shelter for people who fled with nothing Hope in Bangladesh’s Rohingya camps The effort is now well-organised and trucks delivering supplies move up and down the main road between Cox’s Bazar and Teknaf all day long Hope in Bangladesh’s Rohingya camps Only men are in the aid queue, as separate queues are often set up for men and women. Sixty-five-year-old Nur Ahmed wears his ID card which shows he has been formally registered to receive aid Hope in Bangladesh’s Rohingya camps Ajmin Ara, 70, wanders around disorientated. She has lost her entire family and fled to Bangladesh alone; she is painfully thin/skeletal and very weak, but is receiving medical care from a small clinic set up to the side of the aid queue Hope in Bangladesh’s Rohingya camps It’s estimated that 620,000 Rohingya people have fled violence in Myanmar’s Rakhine State in the last three months. Many say they were doing their morning prayers or cooking food when their villages were attacked and they fled, often with only the clothes they were wearing Hope in Bangladesh’s Rohingya camps Nur Asha, 47, sits quietly in the crowd until she can no longer restrain herself and her story comes out in a torrent: how she fled with her son when the military attacked her village but doesn’t know where her other relatives are, how throats were slashed, how children were thrown into fires, how rice paddy fields were filled with bodies left for the dogs to eat Hope in Bangladesh’s Rohingya camps Mohammed Sayed, 24, fled Myanmar about a month ago with his parents, wife and sister after their home was burnt down and many people in their village were killed Hope in Bangladesh’s Rohingya camps Children flock around the queue and one boy has made a hat from an empty medicine package to shield himself from the heat, but other boys playing nearby tease him and knock it off his head and soon it is ripped to pieces Hope in Bangladesh’s Rohingya camps Children who have fled with nothing make toy cars from empty bottles and kites from plastic bags. Despite the horrors they will have witnessed, children still laugh and play for the camera

Tensions in Rakhine have risen since a sweeping Myanmar army operation in August inflamed communal tension and triggered an exodus of over 650,000 Rohingya Muslims to Bangladesh.

“Very sad to hear reports of civilian casualties in Mrauk U... Rakhine urgently needs non-violent rule of law,” Kristian Schmidt, the European Union's Ambassador to Myanmar, said on Twitter.