YANGON, May 13 (Reuters) - Myanmar’s army said on Wednesday it was investigating soldiers filmed beating and threatening to kill suspected insurgents in the western state of Rakhine, where dozens of people have been killed during an upsurge of fighting in recent weeks.

“It is found out that some of the security force members conducted unlawful interrogations,” the army said in a statement posted on its website.

In footage shared widely on social media since Saturday, five men can be seen slumped on the floor of a boat, blindfolded, hands tied behind their backs, as men in military fatigues stamp on their chests and slap and kick their faces. The men whimper and plead that they are civilians.

“I am a civilian, sir,” one says, according to subtitles in the video. “What civilian? Why are you fighting against us?” a soldier shouts, grabbing him by the hair and smacking his cheek. “Let them die, let them break,” says another. One man is hit repeatedly in the face with a shoe.

Reuters could not determine who filmed the video or independently verify its authenticity. The army said the video was shot on April 27 in Rakhine state’s Ponnagyun township.

The military statement said the men who were beaten had been arrested on suspicion of belonging to the Arakan Army, an insurgent group fighting for greater autonomy for the western region. It said they were being transported to the state capital of Sittwe when the beatings happened.

Brigadier-General Zaw Min Tun, a spokesman for the armed forces, known as the Tatmadaw, told Reuters by phone a tribunal had been formed and soldiers had been detained.

Zaw Min Tun said the men who were beaten were connected to the Arakan Army and were being held in Sittwe. He did not specify exactly where, which unit of the security forces was detaining them, whether they had been charged or whether they had legal representation.

Reuters was not able to contact the men or to establish whether they had lawyers. Police in Sittwe did not respond to a request for comment.

The Arakan Army, which Myanmar has designated a terrorist organization, did not immediately comment.

A relative of one of the men in the video said he was not an insurgent. The relative, who asked not to be named for fear of retribution, said the family had met the man at Ponnagyun police station on Tuesday. Police in Ponnagyun did not respond to a request for comment.

The army said the men were from Kyauk Seik, a village where eight people were killed in mid-April. Two local officials and a resident said they were killed in a shelling, but the army said reports that civilians there had been shelled were fabricated.

Government troops have been battling fighters from the Arakan Army, which recruits from the mostly Buddhist majority, for more than a year in Rakhine and neighbouring Chin states.

Dozens of people have been killed and tens of thousands displaced in a recent intensification of fighting, according to the United Nations.

Rakhine state is the region from where 730,000 ethnic Rohingya, members of a Muslim minority, fled to neighbouring Bangladesh during a military crackdown in 2017.

Myanmar is facing charges of genocide at the International Court of Justice in the Hague over the violence, which the army says was a legitimate security operation against Muslim militants.