Baghdad: Photos were posted on a Twitter account claiming to show Sunni militants carrying out a mass execution of captured Iraqi Shiite soldiers, raising the prospect of a broader sectarian war in Iraq.
The photographs, accompanied by captions boasting that up to 1,700 soldiers had been executed, underscored the mounting sectarian animosity fueling the fighting between Sunni extremists and the Shiite-dominated government of Prime Minister Nouri al-Maliki.
The authenticity of the photographs and the insurgents' claim could not be verified, and Iraqi government officials initially cast doubt on whether such a mass execution took place.
There were also no reports of large numbers of funerals in the Salahuddin Province area, where the executions were said to have been conducted.
In one image, men are shown in being transported in trucks. Another image shows armed men wearing black ISIS bandanas pointing their guns toward a clutch of men lying face down in ditch. Still another shows the same men with bloody wounds to their heads.
While the photographs were posted on a Twitter account associated with ISIS, neither the alleged death toll nor the identity of the purported victims could be verified independently.
If the claim is true, it would be the worst mass atrocity in either Syria or Iraq in recent years, surpassing even the chemical weapons attacks in the Syrian suburbs of Damascus last year, which killed 1,400 people and were attributed to the Syrian government.
The latest attack, if proved, would also raise the spectre of the war in Iraq turning genocidal, particularly because the insurgents boasted that their victims were all Shias.
There were also fears that it could usher in a series of reprisal killings of Shias and Sunnis, like those seen in the Iraq war in 2005-7.
The office of the Shias' supreme spiritual leader, Grand Ayatollah Ali al-Sistani, Saturday night issued what amounted to a revision of the ayatollah's call to arms on Friday, apparently out of concern that it was misinterpreted by many as a call for sectarian warfare.
An Iraqi military intelligence official confirmed that the military was aware of the reported executions in Salahuddin Province, which includes the key city of Tikrit, but he did not know how many there were.
He spoke on the condition of anonymity in line with his agency's rules.