Iraq's Shi'ite rulers defied Western calls on Tuesday to reach out to Sunnis to defuse the uprising in the north of the country, declaring a boycott of Iraq's main Sunni political bloc and accusing Sunni power Saudi Arabia of promoting "genocide".
Washington has made clear it wants Prime Minister Nuri al-Maliki to embrace Sunni politicians as a condition of U.S. support to fight a lightning advance by forces from the Islamic State of Iraq and the Levant.
But the Shi'ite prime minister has moved in the opposite direction, announcing a crackdown on politicians and officers he considers "traitors" and lashing out at neighbouring Sunni countries for stoking militancy.
The latest target of his government's fury was Saudi Arabia, the main Sunni power in the Gulf, which funds Sunni militants in neighbouring Syria but denies it is behind ISIL.
"We hold them responsible for supporting these groups financially and morally, and for the outcome of that - which includes crimes that may qualify as genocide: the spilling of Iraqi blood, the destruction of Iraqi state institutions and historic and religious sites," the Iraqi government said of Riyadh in a statement.
Maliki has blamed Saudi Arabia for supporting militants in the past, but the severe language was unprecedented. On Monday Riyadh blamed sectarianism in Baghdad for fuelling the violence.
In the latest bloodshed, scores of Iraqis were killed on Tuesday during a battle for a provincial capital, and fighting shut the country's biggest oil refinery, starving parts of the country of fuel and power.
Government forces said they repelled an attempt by insurgents to seize Baquba, capital of Diyala province north of Baghdad, in fighting overnight. Some residents and officials said the dead included scores of prisoners from the local jail. There were conflicting accounts of how they had died.
ISIL fighters who aim to build a Caliphate based on mediaeval Sunni precepts across the Iraqi-Syrian frontier launched their revolt by seizing the north's main city, Mosul, last week and swept through the Tigris valley towards Baghdad.
The fighters, who consider all Shi'ites to be heretics deserving death, pride themselves on their brutality and have boasted of massacring hundreds of troops who surrendered.
Most Iraqi Sunnis abhor such violence, but nevertheless the ISIL-led uprising has been joined by other Sunni factions, including former members of ousted dictator Saddam Hussein's Baath Party and tribal figures, who share widespread anger at perceived oppression by Maliki's government.
Western countries, including the United States, have urged Maliki