Three US soldiers have been charged with premeditated murder following the shooting of three male Iraqi prisoners.
US soldiers have faced several inquiries into their conduct
They have also been charged over allegations they threatened to kill a fellow soldier if he spoke about the incident, the US military said.
The detainees died during a US military operation near the Thar Thar Canal near Tikrit in northern Iraq on 9 May.
The three soldiers are currently in custody in Kuwait waiting to hear if they will face a court-martial.
Under military law, the maximum penalty for premeditated murder is a death sentence.
The accused soldiers have been identified as Army Staff Sgt Raymond Girouard, Spc William Hunsaker and Pfc Corey Clagett.
They belonged to 3rd Brigade Combat Team of the elite 101st Airborne Division.
The division was at the time involved in operation "Iron Triangle", targeting insurgents active in Salahuddin province and detaining hundreds of people.
The three soldiers are accused of shooting the detainees as they attempted to flee during a US military raid on a former chemical complex, defence officials said on condition of anonymity.
Sgt Girouard: 11 counts
Spc Hunsaker: 8 counts
Pfc Clagett: 6 counts
Charges: Premeditated murder, attempted murder, conspiracy, wrongfully communicating a threat
Source: Reuters news agency
Their unit commander ordered an inquiry on the day the alleged murders took place, apparently after soldiers became suspicious about the circumstances in which the detainees had died.
A criminal investigation began on 17 May and is continuing, the US military said.
According to the charge sheet, each of the three soldiers are also alleged to have separately told Army Pfc Bradley Mason that they would kill him if he testified against them.
The soldiers face four charges: premeditated murder, attempted murder, conspiracy and wrongfully communicating a threat.
They are awaiting the outcome of an Article 32 hearing - the military equivalent of a grand jury - before finding out whether they will face a court martial.
US troops in Iraq have faced several accusations of unlawfully killing civilians and abusing detainees, prompting inquiries into their conduct.
The US military recently began investigating the deaths of 24 unarmed civilians in the town of Haditha last year in an attack blamed on US marines.
The US military appears to have acted quickly to investigate this latest allegation of misconduct, following the accusation that it did not move fast enough to probe the Haditha incident.
But the news that elite American troops are being charged with murder is far from helpful for the US military, says the BBC's Adam Brookes, in Washington.