Twenty militia fighters were killed in clashes with US forces overnight during the "hottest night" in weeks, after cleric Moqtada al-Sadr threatened to declare open war, a US military spokesman said.
Lieutenant-Colonel Steven Stover described a series of gunbattles and air strikes in the Sadr City slum, stronghold of the cleric's Mehdi Army fighters, in which a total of 20 fighters died.
"I would say it's been the hottest night in a couple of weeks," he said. "I think since last night it's pretty much picked up."
He described two separate helicopter missile strikes that each killed three fighters. Nine fighters died in a morning gunbattle and two died in firefights in the evening. Three other fighters died after a roadside bomb they were planting went off, triggering a gunbattle.
In other incidents he described, a roadside bomb on a US convoy killed an Iraqi child, and another bomb strike on a US convoy killed one Iraqi civilian and wounded three.
Hundreds have died in clashes between Sadr's followers and US and Iraqi troops in Baghdad since the government launched a crackdown on the Mehdi Army in the southern city of Basra last month.
Yesterday, Sadr issued a statement threatening "open war" if the government did not end the crackdown.