Tens of thousands of ethnic minority civilians in Burma are being used as forced labourers by the military, according to Amnesty International.
A report by the London-based human rights group says beatings and destruction of homes are also common.
The findings are based on interviews with Burmese exiles in Thailand.
Burma's (Myanmar) military junta has dismissed similar reports in the past, saying their sources are foreign-based opponents of the regime.
The report - Myanmar: Leaving Home - says the military uses people from ethnic minorities to build roads and perform other forced labour.
It said people were ordered to hand over their food and land, and also procure alcohol and young women for soldiers' entertainment.
"Burmese soldiers are forcing a population that is already undernourished to hand over food, land and labour to feed the army," Amnesty International UK Campaigns director Stephen Bowen said.
"Hundreds of thousands of people have been forced to flee Burma as a result."
Amnesty urged Burma to immediately halt the practice of forced labour, describing the situation as "completely unacceptable".
It adds that some villagers were caught between the Burmese military and rebel armies, with both sides demanding food and money from them.
The report is based on interviews with more than 100 Burmese migrants in Thailand.