Iraqi officials yesterday worked to calm soaring tensions after the killing of 70 people at a Sunni mosque, as Washington branded the beheading of an American journalist a "terrorist attack".
And in the latest violence, a suicide bomber detonated an explosives-rigged vehicle at the entrance to the interior ministry's intelligence headquarters in Baghdad, killing six people, officials said.
The attack at the mosque in Diyala province the day before, which most accounts said was the work of Shia militiamen, threatens to increase anger among Iraq's Sunni Muslim minority with the Shia-led government at a time when an anti-militant drive depends on their cooperation. The violence 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.
Deputy National Security Adviser Ben Rhodes said the Foley's beheading "represents a terrorist attack against our country".
Iraq's Sunni parliament speaker yesterday sought to calm sectarian tensions stirred by the mosque attack.
Salim al-Juburi called for political unity and said "the main aim (of the attack) is to foil all the efforts that have been made to form a government".
Premier-designate Haidar al-Abadi, a Shia, has condemned the attack and called for "citizens to close ranks to deny the opportunity to the enemies of Iraq who are trying to provoke strife".
Rights group Amnesty International called Friday's attack a "massacre" and said Iraqi authorities "must properly investigate the unlawful killing of dozens of worshippers".
Army and police officers said the attack on the Musab bin Omair Mosque in Diyala came after Shia 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 machinegun fire, at 70 dead and 20 wounded.
Two officers earlier blamed IS for the attack, saying it had included a suicide bombing, a hallmark of the group, but most accounts pointed to Shia militiamen.
The interior ministry announced an investigation into the attack.
The government turned to militiamen to bolster its flagging forces during an IS-led offensive that has overrun large areas of five provinces since June, but in doing so has encouraged a resurgence of groups involved in brutal sectarian killings in past years.
Meanwhile, US Vice President Joe Biden, writing in The Washington Post, said Washington would back a system of "functioning federalism" in Iraq as a means to breach the divisions in the country.
The United States was prepared to "further enhance" its support for Iraq's fight against IS, he said.
Since launching an air campaign against IS in Iraq on April 8, the US has carried out more than 90 strikes, including three on Friday against militants around Mosul dam, the country's largest.
America's top military officer has said that anti-IS operations in Syria may also be needed.
Foley's killing has stoked Western fears that territory seized by the militants in Syria and Iraq could become a launchpad for a new round of global terror attacks.
Foley, a 40-year-old freelance journalist, was kidnapped in northern Syria in November 2012.
In the execution video, released online, a black-clad militant said he was killed to avenge US air strikes against IS.