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BAGHDAD, June 9 (Reuters) - A suicide truck bomber killed 12 Iraqi soldiers and wounded 30 others in an attack on an army checkpoint south of Baghdad on Saturday, police said.

There was some confusion over whether the huge explosion happened in Jurf al-Sakhar near the predominantly Shi'ite city of Hilla, 100 km (60 miles) south of the capital, or in nearby al-Iskandiriya.

Soldiers were digging through the rubble and the death toll was expected to rise, police said.

A police source said the truck bomber had already passed through one checkpoint before blowing himself up at a second barrier.

Attacks in provinces outside Baghdad have been on the rise since a U.S.-led security crackdown in Baghdad began forcing insurgents out of the capital into surrounding towns and cities.

Iraq's sprial of sectarian violence between majority Shi'ites and Sunni Arabs, dominant under Saddam Hussein, has killed tens of thousands since the bombing of a Shi'ite shrine in Samarra in February 2006 raised fears of civil war.

The crackdown in Baghdad and other areas is a last-ditch attempt to drag Iraq back from the brink of all-out sectarian conflict and to buy time for the Shi'ite-led government to reach political targets set by Washington aimed at promoting national reconciliation.

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