Special forces loyal to Iraqi Prime Minister Nuri al-Maliki were deployed in strategic areas of Baghdad on Sunday night after he delivered a tough speech indicating he would not cave in to pressure to drop a bid for a third term, police sources said.
Pro-Maliki Shi'ite militias stepped up patrols in the capital, police said. An eyewitness said a tank was stationed at the entrance to Baghdad's Green Zone, which houses government buildings.
In a speech on state television, Maliki accused Iraq's Kurdish President Fouad Masoum of violating the constitution by missing a deadline for him to ask the biggest political bloc to nominate a prime minister and form a government.
"I will submit today an official complaint to the federal court against the president of the Republic for committing a clear constitutional violation for the sake of political calculations," said Maliki.
Serving in a caretaker capacity since an inconclusive election in April, Maliki has defied calls by Sunnis, Kurds, some fellow Shi'ites, regional power broker Iran and Iraq's top cleric for him to step aside for a less polarizing figure.
Critics accuse Maliki of pursuing a sectarian agenda which has sidelined Sunnis and prompted some of them to support Islamic State militants, whose latest sweep through northern Iraq has alarmed the Baghdad government and its Western allies.
Washington seems to be losing patience with Maliki, who has placed Shi'ite political loyalists in key positions in the army and military and drawn comparisons with executed former dictator Saddam Hussein, the man he plotted against from exile for years.
A senior U.S. official said on Sunday he fully supported Masoum after Maliki, who the United States has blamed for stoking Iraq's security crisis, criticised him.