Security forces after Wednesday's bomb attack in Kirkuk when 10 Iraqi soldiers died in the ethnically mixed city. Iraq's security forces have lost scores of men in recent bombings

The attack came a day after a car bomb killed 10 Iraqi soldiers in the ethnically mixed city of Kirkuk in the north and marked yet another setback for Iraq's security forces, which have lost scores of men in recent bombings.

The bomber used the tried and tested technique of disguising himself as a soldier -- a simple task in a highly militarised country where many shops sell uniforms and insignia -- and joining the lunch queue. The attack was timed to coincide with the arrival of a new unit, soldiers said. The blast also wounded 50 soldiers.

The explosion occurred in Habbaniyah, to the west of Baghdad in the area known as the Sunni Triangle. Long an al-Qaeda stronghold, the terrorists were driven out over the past two years as local tribes turned on their erstwhile allies, who had tried to ignite a civil war by constantly bombing Shia civilians.

On Wednesday a car bomb in Kirkuk, a tense oil city on an ethnic fault line between Arabs and Kurds, killed 10 soldiers and wounded 22, an attack blamed on Ansar al-Sunna, a local group linked to al-Qaeda. Last week a suicide bomber also disguised in military fatigues blew himself up at a base south of Baghdad where members of an Awakening Group, a tribal militia that had turned on al-Qaeda, were queueing to collect their salaries. Nine militiamen and soldiers died in the blast.

The string of deadly attacks have underscored that while security in Iraq has improved drastically over the past two years, the country is far from stable, with terrorists still capable of causing havoc that could undermine reconciliation efforts between sectarian and ethnic groups after years of war.

Even US troops are vulnerable to the renewed bombings, with five American soldiers killed by a truck bomb at their base in Mosul in the north last week. US commanders have said that their troops may have to stay in Mosul and Baqouba, just north of the capital, beyond a June 30 deadline to withdraw from Iraq's cities because of the threat still posed there by al-Qaeda.