Troops in Myanmar have murdered, tortured and raped civilians since fighting with separatists flared up around nine months ago in northern Kachin State, leading to the displacement of 75,000 people, a rights group said on Tuesday.
Government soldiers had blocked humanitarian aid and attacked innocent people with light and heavy weapons, burning down entire villages, abducting women and forcing children as young as 14 to become porters, according to a report from Human Rights Watch (HRW).
After interviewing more than 100 villagers, victims and army deserters in refugee camps in Kachin and China's Yunnan province, HRW called on Myanmar's government to allow access to aid workers and investigate alleged abuses.
HRW, based in New York, also accused the Kachin Independence Army (KIA) of exacerbating the conflict in the former Burma by using child soldiers and anti-personnel mines and called for international involvement to halt the atrocities.
"The Burmese army is committing unchecked abuses in Kachin State while the government blocks humanitarian aid to those most in need," said Elaine Pearson, HRW's deputy Asia director.
"Both the army and Kachin rebels need to act to prevent a bad situation for civilians from getting even worse.
"Concerned governments should urgently support an independent international mechanism to investigate abuses by all sides to the conflict."
Myanmar's government wants to reach a ceasefire in Kachin as part of moves to end all its decades-old conflicts with separatist armies.
Western countries have made a successful peace process one of their main demands for lifting trade sanctions. Diplomats say the Kachin conflict, which flared up in the middle of 2011 after a 17-year truce, is one of the biggest tests for the year-old civilian government's reform effort.
Talks between the KIA and government peace negotiators have been held on seven occasions since President Thein Sein issued a call for dialogue in August to find "everlasting peace", but they have been fruitless and the KIA says the fighting has reached "total annihilation stage".
Thein Sein has ordered the military not to attack the KIA and use only defensive measures.
Thousands of refugeees have crossed into China to escape the violence. Some in camps along the border told Reuters last month that soldiers were raping and killing.
China told a visiting official from Myanmar in February that maintaining peace and stability in the Kachin border region was in the interests of both countries.
The HRW report, compiled after two visits to nine camps in Kachin States and Yunnan, featured accounts of civilians on the front line who were tortured, forced into labour or were witnesses to the repeated rape of women.
"When we ran, the soldiers shot at us," one woman was quoted as saying. "We were really afraid. We just ran and hid."
(Reporting by Martin Petty in Bangkok; Editing by Alan Raybould)