BANGKOK (AP) — Government helicopters have attacked a school and village in north-central Myanmar, killing at least 13 people including seven children, a school administrator and an aid worker said Monday.

Civilian casualties often occur in attacks by the military government on pro-democracy insurgents and their allies. However, the number of children killed in the air attack last Friday in Tabayin township in Sagaing region appeared to be the highest since the army seized power in February last year, ousting the elected government of Aung San Suu Kyi.

The army’s takeover triggered mass nonviolent protests nationwide. The military and police responded with deadly force, resulting in the spread of armed resistance in the cities and countryside. Fighting has been especially fierce in Sagaing, where the military has launched several offensives, in some cases burning villages, which displaced more than half a million people, according to a report issued by UNICEF this month.

Friday’s attack occurred in Let Yet Kone village in Tabayin, also known as Depayin, about 110 kilometers (70 miles) northwest of Mandalay, the country’s second-largest city.

School administrator Mar Mar said she was trying to get students to safe hiding places in ground-floor classrooms when two of four Mi-35 helicopters hovering north of the village began attacking, firing machine guns and heavier weapons at the school, which is in the compound of the village’s Buddhist monastery.

More than 20 people, including nine wounded children and three teachers, were also taken by the soldiers, she said. Two of those captured were accused of being members of the anti-government People’s Defense Force, the armed wing of the resistance to the military.

Security forces also burned down a house in the village, causing residents to flee.

A volunteer in Tabayin assisting displaced people who asked not to be identified because of fear of government reprisals said the bodies of the dead children were cremated by the soldiers in nearby Ye U township.

“I am now telling the international community about this because I want redress for our children,” Mar Mar said. “Instead of humanitarian aid, what we really need is genuine democracy and human rights.”

Myanmar Now, an online news service, and other independent Myanmar media also reported the attack and the students’ deaths.

A day after the attack, the state-run Myanma Alinn newspaper reported that security forces had gone to check the village after receiving information that the members of the People’s Defense Force were hiding there.

The report said members of the People’s Defense Force and their allies from the Kachin Independence Army, an ethnic rebel group, were hiding inside houses and the monastery and started shooting at the security forces, causing deaths and injuries among village residents. It said the injured were taken to hospitals, but did not mention the situation of the students.

According to the Thailand-based Assistance Association for Political Prisoners, which monitors human rights in Myanmar, at least 2,298 civilians have been killed by the security forces since the army seized power last year.

The UN has documented 260 attacks on schools and education personnel since the coup, the UN Child Rights Committee said in June.