BAGHDAD, Feb 11: Sophisticated Iranian-built bombs smuggled into Iraq have killed at least 170 US and allied soldiers since June 2004, senior US defence officials said on Sunday.

The US officials presented their evidence at a background briefing in Baghdad's fortified Green Zone, after Washington stepped up criticism of Iran.

“Iran is involved in supplying explosively formed projectiles or EFPs and other material to Iraqi extremist groups,” a senior official from the US-led multinational coalition told journalists.

Three coalition officials met reporters to point the finger at the Al-Qods Force of the Iranian Revolutionary Guards Corps, part of Tehran's elite forces accused of links with foreign militants.

“The Qods Force arms extremists and insurgents to carry out terrorist attacks and guerilla warfare,” he said. “The Qods Force provides advice, training and weapons to proxy forces in Iraq.”

The men spoke on condition of anonymity for their security and cameras and recording devices were barred from the briefing, where an array of mortar shells and booby traps were laid out for inspection.

Reporters were issued with a disc containing photographs of alleged Iranian weapons seized in Iraq -- a Misagh-1 ground-to-air missile, EFPs and mortar shells -- showing manufacturing dates in late 2006.

A senior defence analyst said US-led forces had evidence that Iran had stepped up shipments of EFPs, factory-built explosives designed to cut through armour, to armed Iraqi Shia groups.

He said five Iranians arrested in January in the northern Iraqi city of Arbil were Al-Qods force officers who had no diplomatic cover and had tried to flush documents down a toilet as they were arrested.—AFP