A U.S. Army soldier has been charged with 17 counts of murder in the massacre of Afghan civilians during a shooting spree in two villages in southern Kandahar province.

Staff Sergeant Robert Bales was also charged with six counts of attempted murder for the March 11 rampage.

Bales, an 11-year military veteran, is being held at a military prison at Fort Leavenworth, Kansas. He is alleged to have walked out of his southern Afghanistan military post under the cover of darkness and gunned down nine children and eight adults.

Relatives of the victims said Friday they want Bales' trial held in Afghanistan.

He could face the death penalty. The U.S. military has not executed a service member in five decades.

The killings further strained already shaky U.S.-Afghan relations, following a series of missteps, including the inadvertent burning of Qurans at a U.S. military base near Kabul.

Bales' civilian lawyer, John Henry Browne, has said his client was likely suffering from combat stress and post-traumatic stress disorder.

Bales, who served three tours of duty in Iraq before being deployed to Afghanistan last December, suffered a traumatic brain injury in Iraq in 2010. A day before the massacre, he witnessed one of his fellow soldiers get his leg blown off.