A US immigration judge has ordered the deportation of a Liberian accused of presiding over atrocities during the West African country's civil war in the 1990s.

George Boley, 62, the former leader of the Liberian Peace Council, was ordered out of the country by an immigration judge in upstate New York, the first-ever removal under a 2008 law to combat the use of child soldiers.

The ruling on Monday was also based on accusations that Boley had ordered extra-judicial killings during the conflict.

"The United States has always been a place of refuge and freedom from oppression for millions," US Immigration and Customs Enforcement Director John Morton said in a statement.

"We must ensure that those who come here seeking freedom and the rule of law do not have to fear that their persecutor may become their neighbor."

Neither Boley nor his representatives could immediately be reached for comment. He has previously denied allegations of rights abuses.

The government cited "credible reports" that Boley authorized the executions of seven of his soldiers on November 14, 1995.

It cited testimony from Liberia's Truth and Reconciliation Commission (TRC) that Boley's LPC burned dozens of captives it accused of witchcraft and that it massacred 27 people, after raping the women, during an attack on a village.

The atrocities were allegedly committed during the country's two back-to-back civil wars, which ran from 1989 to 2003 and left a quarter of a million people dead.