Rockets slammed into homes in Baghdad just before nightfall today, killing up to 50 people and wounding well over 200, police sources said, adding that the toll could rise as bodies were pulled from the rubble.
The barrage of seven rockets, spread out across various neighbourhoods in the mainly Shia east of the capital, struck as families gathered at evening for the start of the weekend.
"Buildings have been flattened," one police officer said, saying a final death toll was unlikely to be known until daylight. "There are still people trapped."
The mystery attack was the deadliest after several bloody days in the capital when militants have defied a major security crackdown that US commanders hope can start restoring peace.
It underlined the scale of the task facing Prime Minister Nuri al-Maliki, who renewed a confident forecast earlier in the day that his forces would take over control of most of the country from foreign troops by the end of the year.
The salvo came as President George W. Bush began a round of pre-election speeches urging Americans to back a continued US military engagement in Iraq, despite pressure from his Democrat opponents for him to set a timetable to bring the troops home.
An Interior Ministry official put the toll at 46 dead and said hospitals were struggling with 112 wounded. A police source said 43 died and 160 were injured. Neither could say where the Soviet-made Katyusha rockets came from, nor who fired them.
A Web site used by Sunni militants published a statement purportedly from al Qaeda's umbrella organisation in Iraq. It renewed the sort of call for a holy war on the Shi'ite majority that many fear could lead to all-out sectarian civil war.
"O Sunni folks: You have no option but to fight those who label as infidels the companions of your Prophet," the statement attributed to the Mujahideen Shura Council said.
Confirming occupying troops would hand over a second Iraqi province to local security forces next month, Maliki said: "By the end of the year we hope that security in most of the provinces will be handed over."