BAQUBA, Iraq - Washington branded the beheading of a US journalist a "terrorist attack", upping the stakes in its confrontation with jihadists, as Shiite militiamen killed 70 people at a Sunni mosque in Iraq.
The apparent revenge attack at the mosque in Diyala province Friday will increase already significant anger among Iraq's Sunni Arab minority with the Shiite-led government, undermining an anti-militant drive that requires Sunni cooperation.
It came as the US, which is carrying out air strikes in Iraq against Islamic State (IS) jihadists, ramped up its rhetoric over the grisly killing of journalist James Foley, carried out by the group and shown in a video posted online.
In Washington, Deputy National Security Advisor Ben Rhodes said the beheading of Foley "represents a terrorist attack against our country".
Rhodes also said that paying ransoms to free hostages is "not the right policy", confirming Washington's long-standing position amid claims from IS that other countries had paid to have their nationals freed.
In a unanimous statement Friday, the UN Security Council condemned Foley's murder as "heinous and cowardly".
'We found a massacre'
In Iraq, army and police officers said the attack on the Musab bin Omair Mosque in Diyala came after Shiite militiamen were killed in clashes, while other sources said it followed a roadside bomb near one of their patrols.
Doctors and the officers put the toll from the attack, in which worshippers were sprayed with machine-gun fire, at 70 dead and 20 wounded.
Two officers had earlier blamed IS for the attack, saying it had included a suicide bombing, a hallmark of the group, but most accounts pointed to Shiite militiamen.
The government turned to militiamen to bolster its flagging forces during the IS offensive, sparking a resurgence of groups involved in brutal sectarian killings in past years.