A suicide bomber in a flatbed truck laden with 500lbs (220kg) of explosives killed up to 40 people outside a Baghdad police station on Sunday, US military said, citing Iraqi police reports. But Iraqi police and interior ministry sources told Reuters that 22 people had been killed and 25 wounded.
The bloodshed came amid growing tensions over a committee drafting a constitution that is seen as a vital mechanism for drawing Sunnis who form the bulk of the Iraqi insurgency, into a peaceful political process.
Television pictures showed a deep crater in the road as ambulances and firefighters attended the scene. The wreckage of a vehicle smouldered for more than an hour after the blast.
"This is a very cowardly act carried out by criminals, not mujahideen," said a police major who gave his name as Kasim.
"The car bomber made a deliberate decision to attack the police station," said Major Russell Goemaere, spokesman for US 2nd Brigade Combat Team.
"The terrorists undoubtedly see the improved Iraqi police services as a threat to their operations."
CHARTER IN CRISIS?
Overwhelmed by violence, the Iraqi government hopes to give Sunnis more power in a bid to defuse the insurgency and ease sectarian tensions.
But Sunni officials on the constitution-drafting committee say they will not return unless their demands are met.
In Amman, Iraqi Foreign Minister Hoshiyar Zebari said Iraq would finish writing the constitution and hold elections at the end of the year, even if the once dominant Sunni minority continued to boycott the process.
"It is in the interest of the Sunnis to participate without making excuses," Zebari told Reuters.
"If they do not take part, the constitution will not reflect their hopes and ambitions and the process will not stop. There is a timetable and Iraq has to honour international commitments according to UN resolutions," said Zebari, who chaired a meeting of senior Iraqi diplomats in the Jordanian capital.
Zebari's position was firmer than the usual line taken by the Shia-dominated government.
Saleh al-Mutlaq, spokesman for the Sunni National Dialogue Council, said the government could not afford to move ahead with the political process without Sunnis. "My message to brother Zebari is that we are not Sunni members; we are sons of Iraq; we represent a wide proportion of the Iraqi people," he told a news conference.
"We represent more than 42 percent. That's why Zebari or any power on earth cannot sideline this big proportion of Iraqis."
Asked whether Sunnis would accept an Iraqi government investigation into the killing of the Sunnis on the constitutional committee, Mutlaq said: "We believe that the government is not qualified to undertake an investigation that will lead to results that will expose the crime.
"We believe that the nature of the crime points to the involvement of militias in this crime. The accused cannot be the judge."