Mass graves are regularly found in Iraq. Some are recent, some date to Saddam Hussein's era
Security forces in Iraq have found a mass grave containing about 100 decomposed bodies.
The grave, discovered in Khalis, north of the capital, Baghdad, is one of the largest such finds in several months.
Iraqi and American officials said it was not clear who was responsible, but the grave may date back to sometime before the 2003 US-led invasion.
A US military spokesman said the bodies were mainly skeletal, indicating they may have been there a long time.
Iraqi army officer Major General Abdel Karim al-Rubaie added that the victims were beyond recognition.
"We can't identify them," he told AFP news agency. "There are just bones in there. At the moment we have left the remains in the grave itself."
Human rights groups believe there are many such mass graves in Iraq where thousands of people killed during the regime of deposed president Saddam Hussein were buried.
Hundreds of Iraqis have also died in sectarian fighting since the invasion and more recent mass graves are regularly discovered.
The US and Iraqi authorities often blame al-Qaeda for the killings.
In February, a grave with about 50 bodies was found near Samarra, 100km north of Baghdad, during a hunt for al-Qaeda militants, Reuters reported.