"Most of the 107 [mm] rockets we see are Chinese manufacture, Chinese origin," Maj. Marty Weber told a U.S. military briefing in Baghdad on April 11. "But what we see is, we will see Iran buy them, and then they will repaint them, remark them and then sell them on the open market for themselves."

The officials said the weapons were refurbished and then provided to Shi'ite and some Sunni insurgents in their war against the U.S.-led coalition.

Iran has also sent its own weapons to insurgency groups in Iraq, officials said. They cited the 81 mm mortar, manufactured in Iran, Middle East Newsline reported.

Weber, an officer from the U.S. Army's 79th Explosive Ordnance Disposal Unit, displayed Chinese weapons said to have been manufactured in 2005. He said Iran has been an importer of Chinese ordnance.

"Most of this region uses 82 mm mortar rounds, not 81 mm mortar rounds," U.S. military spokesman Maj. Gen. William Caldwell said.

Iran has also smuggled weapons made in Bulgaria to insurgency groups in Iraq. Officials cited rocket-propelled grenades and light ammunition, which they said contributed to a rise in U.S. casualties.

"We do have an increase that we have seen, obviously, in coalition force casualties that have occurred over the last 30 days," Caldwell said. "And it's something we anticipated could occur as we had more forces down inside the city and greater numbers than previously were operating there before. So we knew that was a possibility."