The Arakan Army (AA) is engaged in a fierce fight with the military for control of Rakhine, where it has seized swaths of territory in the past year, all but cutting off the state capital Sittwe.

The Rakhine conflict is one element of the bloody chaos that has engulfed Myanmar since the military ousted Aung San Suu Kyi's civilian government in a 2021 coup, sparking a widespread armed uprising.

The AA posted on its Telegram channel that a military jet bombed a detention area in Mrauk-U Township around 4.45 pm (10:15 GMT) on Saturday, where family members of junta soldiers were being held by the AA.

"Those who were killed and wounded were family members of soldiers in Myanmar's Army. We arrested them during fighting," the AA said in the post.

"As we were preparing a plan to release them, they were bombed," the AA said.

Nine children were among those dead, including a two-year-old boy, it said.

The others killed were women, according to a list of the dead posted by the AA.

Photos of the aftermath posted on the Telegram channel showed a long row of bodies laid on the floor in a grassy area, covered in white sheets. A number of people could be seen grieving close by.

AFP has attempted to contact the junta for comment about the incident but calls have not been answered.

The military is struggling to fight opposition to its rule on multiple fronts around Myanmar and it has been regularly accused of using air and artillery strikes to hit civilian communities.

It is unclear whether the strike in Mrauk-U Township was mistargeted or if the junta was unaware the area was being used as a detention site for soldiers' families.

As well as youth-led "People's Defence Forces" that emerged to oppose the coup, the military is also battling numerous long-established and well-armed ethnic minority armed groups.

These groups, which include the AA, control large areas of territory along Myanmar's borders.

The UN Development Programme warned in November that Rakhine was heading towards famine as fighting squeezed commerce and agricultural production.

The United Nations said this month more than 3.5 million people have been displaced by the conflict in Myanmar, an increase of 1.5 million from last year.