Looking for His glorious appearing! Titus 2:13

Iraqi Prime Minister Nouri al-Maliki wants to hold on to power. Photo: AP

Baghdad: Special forces loyal to Iraqi Prime Minister Nouri 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.

A bloc comprising Iraq's biggest Shiite parties is close to nominating a prime minister, the deputy speaker of parliament said on Monday, directly challenging Mr Maliki.

Haider al-Abadi's comments in a tweet came after police sources said special forces and Shiite militia loyal to Mr Maliki had been deployed in strategic areas of Baghdad.

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, Mr Maliki accused Iraqi President Fouad Masoum, a Kurd, 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 Mr Maliki.

Serving in a caretaker capacity since an inconclusive election in April, Mr Maliki has defied calls by Sunnis, Kurds, some fellow Shiites, regional power broker Iran and Iraq's top Shiite cleric for him to step aside for a less polarising figure.

The troop movements have raised speculation that they may mark the start of a coup by Mr Maliki to take full control of the government.

A western security expert based in Iraq said that Mr Maliki deployed militia and elite special forces units around the International Zone prior to giving the speech.

"He was clearly anticipating a negative, possible coup-like response," said the expert, whose employer does not allow him to speak openly to the media.

Critics accuse Mr Maliki of pursuing a sectarian agenda which has sidelined Sunnis and prompted some of them to support militants from the Islamic State of Iraq and the Levant, whose latest sweep through northern Iraq has alarmed the Baghdad government and its Western allies.

Washington seems to be losing patience with Mr Maliki, who has placed Shiite 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 US official said on Sunday he fully supported Dr Masoum after Mr Maliki, who the United States has blamed for stoking Iraq's security crisis, criticised him.

"Fully support President of Iraq Fouad Masoum as guarantor of the Constitution and a [prime ministerial] nominee who can build a national consensus," Deputy Assistant Secretary of State Brett McGurk, the US State Department point man for Iraq, said on his Twitter feed.

US President Barack Obama urged Iraqi politicians on Saturday to form a more inclusive government that can counter the growing threat from ISIL, which recently changed its name to Islamic State and declared a "caliphate".

But Mr Maliki keeps digging in.

"Now we can see unprecedented deployment of army commandos and special elite forces deployed in Baghdad, especially sensitive areas close to the green zone and the entrances of the capital," one of the police sources said. "These forces are now taking full responsibility of securing these areas of the capital."

Iraq's Interior Ministry has told police to be on high alert in connection with Mr Maliki's speech, a police official said.

ISIL militants have capitalised on political deadlock and sectarian tensions that have made it easier for the group to make fresh gains after arriving in the north in June from Syria.

The group, which sees Shiites as infidels who deserve to be killed, has ruthlessly moved through one town after another, using tanks and heavy weapons it seized from soldiers who fled in the thousands.

ISIL militants have killed hundreds of Iraq's minority Yazidis, burying some alive and taking women as slaves, an Iraqi government minister said on Sunday, as US warplanes again bombed the insurgents.

Human rights minister Mohammed Shia al-Sudani accused the Sunni Muslim insurgents - who have ordered the community they regard as "devil worshippers" to convert to Islam or die - of celebrating what he called a "a vicious atrocity".

No independent confirmation was available of the killings of hundreds of Yazidis, bloodshed that could increase pressure on Western powers to do more to help tens of thousands of people, including many from religious and ethnic minorities, who have fled the militants' offensive.