David Rodriguez (File photo)

The U.S. military says hidden explosive devices are the most common weapon used by insurgents in Iraq. Officials have said attacks on military supply convoys using the improvised explosive devices, or IEDs, have doubled in the past year. But in northwest Iraq, where insurgent resistance has been fierce, the local U.S. commander says IED attacks have decreased in the last three months.

U.S. Major General David Rodriguez says IED attacks in recent months have been fewer, less sophisticated and less lethal. He says the attacks have decreased both in number and in effectiveness by about 20 percent, partly because of tips from local Iraqis and successes against the insurgent leadership, but also because of several technological advancements.

"We have robots, we have electronic countermeasure devices," said General Rodriguez. "We have Buffalos that have long arms that provide a standoff."

The heavily-armored Buffalos are 23-ton vehicles designed to find IEDs. Troops inside the vehicle sit more than three meters above the road and use a long robotic arm equipped with a video camera to probe for explosives. Once an IED is located, explosive ordinance teams are called in to defuse or destroy the device.

General Rodriguez also said coalition forces continue to capture foreign militants in northwest Iraq, most of whom are believed to have come across the Syrian border.

"I can tell you the people we have caught were involved in some of the suicide bombings over the last several months," he said.

The general says in the last three months about 70 foreigners have been captured and another 100 were either killed by coalition or Iraqi forces or died in suicide attacks.