Iraqi Prime Minister Nouri al-Maliki has said that he intends to file a complaint against President Fuad Masum for violating the constitution.

"Today I will file a formal complaint to the federal court against the president," he said, in a televised speech likely to deepen political tensions in the country.

In his speech, he also indicated that he would not drop his bid for a third term in office.

Maliki, seen as an authoritarian and sectarian leader, has defied calls by Sunnis, Kurds, some fellow Shi'ites and regional power broker Iran to step aside for a less polarising figure who can unite Iraqis against fighters of the Islamic State group, whose advance in the north has rattled the Baghdad government and its Western allies.

Special forces loyal to Maliki were deployed in strategic areas of Baghdad, police said, after he gave the tough speech on television.

Several police sources also said the forces had taken up positions at key entrances to the sprawling capital.

Meanwhile, Kurdish fighters, bolstered by US air strikes, retook two towns from Sunni fighters of the Islamic State group.

Kurdish peshmerga fighters were able to push the Islamic State group out of the villages of Makhmour and al-Gweir, some 45km from Erbil, Brig. General Shirko Fatih said.

The United States launched a fourth round of air strikes on Sunday on Erbil as part of efforts to blunt the fighters' advance and protect American personnel near the Kurdish capital.

US warplanes and drones have also attacked fighters firing on minority Yazidis around Sinjar, which is in the far west of the country near the Syrian border.