A parked car bomb killed 25 people and wounded 115 last Thursday, three days after three separate bombs killed another 13 people in the same district.

The latest attack comes as new figurers show at least 1,652 civilians were killed in Iraq in July, one-third more than in the previous month.

According to figures compiled from three Iraqi ministries and seen by AFP news agency, July's toll is also slightly higher than the number for February, when the US launched a "surge" aimed at reducing sectarian violence in the country.

In that month, 1,626 civilians were killed according to the ministries' figures.

In June, 1,241 were killed, prompting hope that the troop reinforcements were having an effect, but July's figure represents a 33 per cent increase in the number of deaths.

Political reconciliation

Meanwhile, a senior US military official has said that while the deployment of US troops has improved security in Iraq to some degree, the country's future is jeopardised by the failure of Iraqi leaders to forge political reconciliation.

Navy Admiral Michael Mullen told a senate hearing that security on the ground in Iraq is "not great, but better".

But Mullen said the US military effort could succeed only if Iraqis struck a compromise to defuse sectarian divisions.

"Barring that, no amount of troops and no amount of time will make much of a difference," he said.

Mullen is expected to be approved as the most senior military adviser to George Bush, the US president.

Mullen also said that an early withdrawal of US troops could turn Iraq into a "cauldron".