A car bomb has killed up to 33 people and wounded another 25 in a market about 75km north of the capital Baghdad, according to officials

The blast occurred near a police checkpoint in the village of Yathreb near the town of Balad on Sunday, a police official in Salaheddin province said.

"It was a suicide car bomber. The attack took place at 4:30pm [1330GMT] when the market was very busy," Colonel Issa Ayan said.

The bomb reportedly caused havoc in the market and destroyed a number of buildings.

The death toll could rise as some bodies are thought to be buried beneath the rubble, and some people have been reported missing after the explosion, Ayan said.

Salaheddin is one of the provinces in which the US and Iraqi forces launched Operation Phantom Phoenix, a major offensive against al-Qaeda fighters which began on January 8.

The attack came as Robert Gates, the US defense secretary, arrived in Iraq to discuss security in the country and to prepare talks on a pact that would define future relations between Washington and Baghdad.

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A map of Iraq