Women from the Shan minority and other ethnic minority groups in northeastern Myanmar are telling stories of rapes by the military that are sometimes characterized by sadism and that human rights groups say appear to be authorized and systematic.
The US State Department investigated the reports, which it called "appalling," and said it found them credible.
The military government has denied that rape is tolerated, asserting that any perpetrators are harshly punished, and calling the reports fabrications by domestic and foreign enemies of their government.
"Isolated rape cases may have happened in certain areas, as is happening in many other countries around the world," the Myanmar government said in a statement last month. "But `systematically using rape as a weapon of war' is just too ridiculous."
Minister for Labor U Tin Win, said this was the first time the military had ever been accused of such abuses.
"Severe punishment is always handed down to any member of the armed forces who rape women, be they officers or other ranks or privates," he said.
"The Myanmar society upholds very high standards of decency and culture under the all-encompassing fold of Buddhist teachings," he said.
However, the reports have been supported by widespread and consistent descriptions given by victims and witnesses, including members of separate ethnic groups.
The government must contend with three separate and mutually corroborating reports -- the initial collection of accounts by a Shan human rights group a year ago, an unusual follow-up investigation by the State Department and, most recently, a report by an independent human rights group.
"Women are raped during forced labor assignments, they are raped while farming, they are raped in their own homes and raped also when they are trying to flee to Thailand," said Veronika Martin, an author of the most recent study, by the human rights group Refugees International, based in Washington.
That report, released last month, made the point that the allegations came from a range of ethnic groups and that the rapes -- sometimes conducted on military property by high-ranking officers -- appeared to be officially sanctioned.
It documented accounts of 43 rapes among women from the Karen, Karenni, Mon and Tavoyan groups as well as the Shans. It said 75 percent of the women interviewed reported knowing someone who had been raped.
"Aside from the fact that rapes are happening across ethnic boundaries, our report also showed that rape is happening on a widespread basis and is not the result of rogue groups or occasional unruly soldiers," Martin said.
Because military units are often stationed near villages for long periods and use local people as forced laborers, the report said, three-fourths of the women interviewed were able to identify their attackers by their battalion number.
The initial allegations were made last year by the Shan Women's Action Network, a private human rights group based on the Thai-Myanmar border, which described rape as a systematic weapon of war.
Its report said it had documented 173 incidents of rape or sexual violence against 625 women and girls committed by soldiers from 52 military battalions between 1992 and 2001.
It alleged that 25 percent of the rapes resulted in death and that 83 percent were committed by officers.