The attack came as US Vice President Dick Cheney made an unannounced visit to Baghdad to urge Iraqi leaders to speed a process of national reconciliation.

The Arbil blast tore a two meter (yard) deep crater in front of the autonomous northern region's interior ministry, scattering the bodies of dead and injured outside the heavily guarded building.

Kurdistan's health minister, Zirian Abdelrahman, said 19 were people killed, although his colleague at the interior ministry later gave a lower toll.

"It was a truck bomb carrying cleaning products that targeted our ministry and killed 14 people and wounded 87, including government employees," regional interior minister Karim Sinajri told journalists.

The blast site was a scene of chaos as rescue workers rushed to evacuate the wounded. Few panes of glass were left intact in nearby buildings and children's shoes lay scattered in the rubble.

Suspicion fell immediately on Ansar al-Sunna, an extremist Islamist group that grew out of the Kurdish Ansar al-Islam movement and is active in northern parts of the country.

While insurgent car and truck bombings are an almost daily scourge in central Iraq, this was a rare incident in the Kurdish autonomous region, which has been spared the bulk of Iraq's sectarian violence and insurgent attacks.

In May 2005, a suicide bomber killed 46 people in Arbil, but otherwise the three predominantly Kurdish provinces have been largely peaceful.

The blast struck a blow at the Kurdish region's carefully constructed image of being a unique peaceful haven amid Iraq's ongoing chaos.

A backwater under former leader Saddam Hussein with little investment, the economy in the three Kurdish provinces has been booming with a steady flow of construction and foreign investment over the past four years.

The night before the blast, US undersecretary of defense Paul Brinkley was visiting the city with a delegation of 20 US businessmen to showcase the region and encourage investment.

"This is a chance for Western investors to see the stable regions in Iraq for the purpose of investments," he told journalists at a press conference.

In Baghdad, violence raged on with the assassination of a high ranking official in the housing ministry and the killing of a construction worker building a controversial wall around the Sunni neighbourhood of Adhamiyah.

US military spokesman Major General William Caldwell told reporters that after dropping by two thirds due to a massive security operation in the capital, assassinations and executions were on the rise again.

"There has been a slight uptick in the last two weeks in the number of murders and executions observed in Baghdad," he said.

Both the Iraqi and US commands refuse to reveal the figures upon which they base such reports. An interior ministry official, speaking on condition of anonymity told AFP that 25 bodies were found on Tuesday alone.

The US military denied reports that a helicopter gunship fired on a primary school north of Baghdad but confirmed at least two children were killed in an attack on insurgent bombers.

Helicopters fired at militants planting a bomb Tuesday near an illegal checkpoint, but afterwards when US forces arrived in the area, they were told that five bystanders, two of them children, were killed as well.

Air Force Major General David Edgington said they were certain about the target as it was first observed by unmanned aircraft.

"They were watching them emplace the IED (bomb) so there was absolutely no question," he said, adding that there would be an investigation into the civilian deaths.

In the central Iraqi city of Samarra, insurgents destroyed two police stations belonging to the National Police just days after a deadly assault left 12 policemen dead, including their chief.

Cheney, meanwhile, made a surprise visit to Baghdad to warn top Iraqi leaders that US patience with their faltering attempt is running short.

"There's a lot going on. This is a very important time. There's a lot to talk about," Cheney said as he met with US Ambassador to Iraq Ryan Crocker and the top commander of US forces in Iraq, General David Petraeus.