Yangon (Reuters) - Myanmar said at least nine police officers were killed and four were wounded Sunday in multiple assaults on border guard posts along the Southeast Asian nation’s troubled frontier with Bangladesh.

Eight attackers, identified only as “insurgent terrorists,” but believed by officials to belong to a Muslim group, were killed and two were captured alive in clashes in the western state of Rakhine since the early hours of Sunday, national police chief Zaw Win told a press conference.

Rakhine is home to about 1.1 million members of the mostly Muslim Rohingya ethnic group, most of whom are denied citizenship and face severe restrictions on their movements.

About 125,000 people, most of them Rohingya, have been displaced since 2012 when intercommunal violence left more than 100 people dead in Rakhine.

A state official told Reuters he believed Sunday’s assailants belonged to the Muslim group.

The attacks began at 1:30 a.m. on Sunday when some 90 assailants stormed a police force office in Kyiganbyin village, Maungdaw Township, Zaw Win told reporters in the capital, Naypyitaw.

The attackers killed six police officers, wounded two others and seized 51 weapons and more than 10,000 rounds of ammunition in the initial attack, he said.

According to Zaw Win, a simultaneous attack on a border police camp in Kyeedangauk village, Rathidaung Township, also killed one police officer and wounded two others.

A third incident took place in Buthidaung Township at 4:30 a.m., leaving two more police dead and one missing, he said, adding that seven alleged attackers were killed in that clash.

Zaw Win did not speculate on the possible identity of the attackers.

But a senior Rakhine State government official who asked not to be named said he believed they were “Bengali,” a term used by many in Myanmar to refer to the Rohingya that suggests they come from Bangladesh.

The official said he based his judgment on photographs purported to be of the captured attackers -- which Reuters has seen but could not verify -- that appeared to show two men of South Asian descent restrained with belts.

“But we just don’t know for sure yet which organization they belong to,” the official said.

Authorities on Sunday issued an order that imposes a 7 p.m. to 6 a.m. curfew and prohibits gatherings of five or more people in Maungdaw Township.

The attacks represent the most deadly violence in Rakhine State since 2012, but a spate of smaller attacks on border police took place in 2014.

A report by the International Crisis Group said there was no evidence to support the government’s claim at the time that a group known as the Rohingya Solidarity Organisation (RSO) was responsible.

Independent observers have long said the RSO, which was formed in 1982, is practically defunct.

However, the 2014 report said, “there appear to be efforts underway in the wake of the 2012 violence to rehabilitate the group as an armed organization.”