Myanmar's army is continuing to use rape as a weapon of war, according to a report by the Women's League of Burma (WLB).

Since the new supposedly civilian government took office in Myanmar in 2010, the WLB has documented 104 women who have been victims of sexual violence by the army.

"Sexual violence is the most assaulting [violation] to women's dignity and the most obvious result of Burma's patriarchal culture that subjects women to violence," the report said.

"The nature of the acts and the way they are conducted show patterns confirming that rape is still used today as an instrument of war and oppression against the ethnic population... Sexual violence is used as a tool by the Burmese military to demoralize and destroy ethnic communities, in an attempt to establish dominance over them."

Among the victims were girls as young as 8 or 9. The latest documented case involved a girl of 15 who was gang raped by three Burmese soldiers.

The WLB believes that the report represents only the tip of the iceberg as many areas affected by conflicts are very hard to reach in order to obtain testimonies from victims while others have been threatened by their attackers to remain silent.

In many cases women were victims of gang rapes. This signifies, according to the report, that soldiers feel confident of committing these crimes openly and will go unpunished.

The crimes are mainly perpetrated by high-ranking military officials, added the report, and few if any incidents are brought to justice.

According to the WLB, sweeping reforms are necessary in order to eliminate sexual violence which has become institutionalised as opposed to random attacks by rogue soldiers.

The 2008 constitution has also to be amended to ensure that the military is placed under civilian control.

The US State Department urged the Myanmar government to investigate all allegations of rape.

"Despite tremendous progress in Burma over the past three years, significant challenges remain, including further improving the country's overall human rights situation," State Department spokeswoman Marie Harf said.

Myanmar's government denied rape is used as a means of war.

"It's not the policy of our Tatmadaw (military) to use rapes as weapons," presidential spokesman Ye Htut told news agency Reuters.