BAGHDAD: A car bombing devastated a food market in the city of Kirkuk, killing at least 27 people. The early evening attack, which bore the hallmarks of Sunni extremist groups like al-Qaida in Iraq, was the second in the Kirkuk area since a truck bombing killed 82 people on June 20.

The latest blast was a deadly example of the violence many Iraqis fear will increase with the departure of US troops from urban areas, despite Prime Minister Nouri al-Maliki's confidence in Iraq's nascent security forces.

The bombing came hours after US military announced that four American soldiers were killed in combat shortly before the military completed their withdrawal from Iraq's cities on Monday.

It was the deadliest attack on US forces since May 21, when three soldiers were killed and nine wounded in a roadside bombing in Baghdad.

'It reminds me that there are still dangers out there,' Gen. Ray Odierno, the top US soldier in Iraq, said of the American deaths. 'There are still people out there who do not want the government of Iraq to succeed.'

The violence marred what otherwise was a festive occasion as Iraqis commemorated the newly declared National Sovereignty Day with military parades and marching bands in the capital.

Iraqi authorities welcomed the US pullback with nationalist rhetoric and celebrations in what appeared to be an attempt by al-Maliki to rally the public behind his government and secure more support ahead of an election in January.

Al-Maliki, whose three years in office saw a dramatic decline in violence, used a nationally televised address to project an air of confidence.

'Those who think that Iraqis are incapable of protecting security in their country and that the withdrawal of foreign forces will leave a security vacuum which will be difficult for Iraqi forces to fill are making a grave mistake,' the prime minister said.

In Washington, President Barack Obama declared Tuesday that 'Iraq's future is in the hands of its own people,' warning of more violence in the days ahead but signaling optimism that Iraq will prevail as a stable, sovereign nation.

'The Iraqi people are rightly treating this as a cause for celebration,' Obama said. 'The future belongs to those who build, not to those who destroy.'

Obama predicted new flare-ups of violence, citing the ''senseless bombing' in Kirkuk, the latest in a series of attacks that have killed close to 300 people since June 20.

'Make no mistake,' Obama said, 'there will be difficult days ahead.'

At a news conference, Odierno charged that Iran was continuing to support and train militants in Iraq who attack US and Iraqi forces with rockets and roadside bombs.

'They have not stopped and I don't think they will stop,' Odierno said. 'I think many of the attacks in Baghdad are from individuals that have been in fact funded or trained by the Iranians.'

The US pullback is a significant step toward the final American withdrawal from Iraq by the end of 2011, a deadline set by a US-Iraqi security agreement. -AP