The No 2 US commander in Iraq today said a 7-month-old security operation has reduced violence by 50% in Baghdad but he acknowledged that civilians were still dying at too high a rate.

A roadside bomb struck an Iraqi police patrol today, killing one officer and wounding four others and a civilian, a police official said.

Apparently seeking to calm fears that he will not go after militia gunmen loyal to one of his key political backers, Iraqi prime minister Nouri Maliki said 400 fighters from the Mahdi Army had been arrested over the past several weeks.

A series of explosions and shootings rocked Baghdad this morning, killing at least 19 people and wounding dozens, police have revealed.