Iraqi police say US helicopters are engaging Shiite militants in
Baghdad's embattled Sadr City district.
Two people have been killed and 12 injured in clashes between joint Iraqi-American forces and fighters of the Mahdi Army of cleric Muqtada al-Sadr.
The sprawling district with over two million inhabitants has seen continuous clashes between Shiite militants and Iraqi and US forces in the past month.
Elsewhere in Baghdad, police say a suicide bomber blew up a security checkpoint in the eastern neighbourhood of Zayouna killing two Iraqi soldiers and injuring five.