Unknown gunmen opened fire at the convoy of Iraqi President Adel Abdul Mehdi in western Baghdad on Thursday, said an interior ministry official.
"Mehdi was with the convoy when the gunmen attacked, but it was not known whether there was any casualty," the official said on condition of anonymity.
He said: "We have just called in a US military support according to an urgent demand from Mehdi's lieutenant who said they were surrounded by the attackers."
It was not clear whether Mehdi was hurt in the attack, he added.
In a separate incident, a car bomb went off near an Iraqi army patrol almost at the same area, causing undetermined casualties, a well-informed police source said.
"A car bomb parked near the Nafaq al-Shurta (police tunnel) area detonated at about 11:20 a.m. (0820 GMT) near a passing Iraqi army patrol," the source said.
It was not clear whether there was any casualty as the Iraqi army guarding the area cordoned off the scene, he said.
However, witnesses said an Iraqi army Humvee was ablaze.