A car bomb has exploded in a crowded commercial district of the southern Iraqi city of Basra, killing at least 20 people and wounding at least 40.
The explosion occurred in the busy Algiers Street area of the city as crowds flocked to shops and restaurants after the daily Ramadan fast.
It appears to have targeted a police patrol, and reports say six officers were among the dead.
Basra, Iraq's second city, is under the control of British forces.
Although car bombings are common in central and northern Iraq, the south, predominantly populated by Shias, has been comparatively peaceful.
However, there has been a recent upsurge in attacks in the region.
The car bombing happened at about 2030 local time (1730 GMT).
At least four cars were totally destroyed by the blast, an AFP news agency photographer at the scene said.
Another explosion, thought to have been caused by a rocket-propelled grenade, followed soon afterwards, close to the British forces' base in the city.
The BBC's David Willis, in the capital Baghdad, says recent months have seen an increase in sectarian violence in Iraq, with Sunni insurgents virtually declaring war on Shias.
A recent Pentagon report said that about 26,000 Iraqis had been either killed or injured in attacks by insurgents since January 2004.
Senior US officer killed
Last week's military casualties included the highest-ranking American soldier killed in action in the Iraq conflict, the US military said on Tuesday.
Col William Wood, 44, commanding officer of the 1st Battalion, 184th Infantry Regiment, was killed by a roadside bomb in Baghdad on 27 October.
The soldier from Florida had not been told before he died that his promotion from lieutenant colonel to colonel had been approved.
"It validates his career," Wood's half-brother Donald Hansen told the Associated Press.
"It's proper for the Army to do what they've done."