The U.S. called on Myanmar to investigate the killings of two ethnic Kachin teachers, amid allegations by activists the women were raped and murdered by government forces.

The bloodied corpses were discovered earlier this week in a village in northern Shan state.

A medical report indicated the volunteer teachers for the Kachin Baptist Convention died from penetration wounds to their liver, lungs and head, Zau Ra, secretary of the organization, told The Associated Press by telephone Thursday.

Their private parts also had been violated, he said, adding he was "shocked and saddened' by the news.

Myanmar, also known as Burma, was under dictatorship until 2011, and President Thein Sein's nominally civilian government has spearheaded the country's bumpy transition toward democratic rule. With many of his early reforms now stalled or sliding backward, he is trying to end decades-long civil wars in resource-rich border regions before his term ends later this year.

The military — which in recent days has launched fresh attacks in Kachin state, trapping more than 1,000 civilians in several villages — has long been accused of serious abuses in fighting against ethnic rebels.

Activists say they two teachers were raped and killed by government forces.

State Department spokeswoman Jen Psaki on Wednesday called on Myanmar authorities to bring the perpetrators to justice. She said Myanmar has told the U.S. it is looking into the case, and the facts of what happened are still being determined.

The deaths come a week after the U.S. held a human rights dialogue with civilian and military officials in Myanmar.

"This is the first time that our religious staff have been attacked," Zau Ra of the Kachin Baptist Convention told The AP from the town of Muse, about 10 miles (16 km) from where the bodies were found Monday.