Human rights advocates are accusing the Burmese army of using prison inmates as porters on the front lines of its conflict with ethnic militias.

U.S.-based Human Rights Watch and the Burmese-based ethnic Karen Human Rights Group released a joint report Wednesday detailing the alleged abuses, which they describe as war crimes. The report is based on interviews with 58 ex-porters who escaped military operations in the Karen and Pegu regions between 2010 and 2011.

The men described various atrocities carried out by the military, saying they witnessed or endured summary executions, torture and beatings. They also said prisoners were used as human shields to set off landmines or protect soldiers from enemy fire.

The convicts said they were also denied medical attention and adequate food and water.

Burma's military has been accused in the past of forcing both prisoners and civilians to serve as porters. But Elaine Pearson, the deputy Asia director for Human Rights Watch, said the “press-ganging” of prisoners into front-line duty “raises the Burmese army's cruelty to new levels.”

The groups are urging concerned governments to support calls for a United Nations-led inquiry into violations of Burmese and international human rights laws.