Until a year ago, the town and its surrounding countryside was a lawless region, a haven for al-Qaeda fighters and a hideout for weapons smugglers.

Since then, al-Qaeda forces have been largely pushed out, by joint US and Iraqi military operations.

But the smugglers are still coming through, bringing in rockets, explosives, bomb-making equipment and expertise across the border from Iran.

“They could be moving stuff to go down to either Sadr City, Baquba or Baghdad,” said Lt Luke Brown, scanning the countryside through his night-vision goggles.

The American Stryker armoured vehicles are fitted with sophisticated infrared and thermal imaging technology, not at the disposal of the Iraqi police and army.

But despite their hi-tech equipment, so far the Americans are having little luck.

Iranian weapons

“We do know that a lot of the arms, ammunitions and explosives that we find here, being used against the Iraqi security forces, our forces and against the Iraqi people clearly have originated from Iran,” says Col David Funk.