A newborn baby was one of at least 14 children and adults killed when a suicide bomber detonated a lorry laden with explosives close to a primary school in the northern Iraqi city of Kirkuk yesterday.

The latest massacre of Iraqi children came as 21 Shia market workers were ambushed, bound and shot dead north of the capital. The victims came from the Baghdad market visited the previous day by John McCain, the US presidential candidate, who said that an American security plan in the capital was starting to show signs of progress.

The Kirkuk bloodshed erupted when a bomber driving a truck full of explosives hidden by sacks of flour targeted an Iraqi police station that US soldiers were visiting. The full force of the blast hit a nearby primary school.

Buthayna Mahmud, 10, was horrified to see the bodies of her classmates strewn on the ground in flames. “Everyone I saw was wearing the blue school uniform drenched with blood. Some of their dresses were torn. I only saw fire. I heard teachers and students shouting,” she said. “When we rushed out of the school, we saw pupils on the ground, some of them burning.”

“We were at the last lesson and we heard the explosion. I saw two of my classmates sitting near the window. They fell on the floor, drenched in blood,” said Naz Omar, a girl in the fifth form. “They could not speak. I was terrified. I said, ‘God is Great. I need my mother. I need my father’.”

Terrified children fled the carnage in the ethnically mixed city of Kurds, Turkomans and Arabs, many of whom were settled there by Saddam Hussein in an attempt to “Arabicise” Kirkuk and “ethnically cleanse” it of Kurds. Local observers said that the death toll among the school children would have been worse if most of the pupils had not been inside when the bomber struck.

Terrorists in Iraq have frequently killed large groups of children, either while aiming at nearby American or Iraqi security forces or as an end in itself. US forces said last month that two children had been used by terrorists to sneak a car bomb through a checkpoint and it had been detonated while they were still inside.

As well as the killings of the children and the Shia market vendors, four people were blown up by another suicide bomber at a police checkpoint in Baghdad, while a roadside bomb killed four civilians in a Shia town just north of Baghdad. Yet another roadside bomb killed an Iraqi soldier and wounded seven others near the Iranian border. The US announced the deaths of six of its soldiers at the weekend.

More than 600 Iraqis have been killed in the past week despite a US-Iraqi security plan to quell violence in the capital. Most of the killings have been the result of truck bombs outside Baghdad.

Mr McCain said that the situation was showing signs of improvement and blamed waning support in the United States for the war on the media, which were portraying an overly negative image of the crisis.

Kirkuk is seen as a potentially explosive fault line between various ethnic and religious groups because it sits on a vast reserve of crude oil and is claimed by the Kurds as part of their autonomous northern region. Their claims have elicited fears from Sunni Arabs that the Kurds and the Shia, who control the oil-rich south, are trying to cut the once-powerful Sunni minority out of the country’s mineral wealth.

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