WASHINGTON —  Some weapons entering Iraq are coming from Iran, Defense Secretary Donald H. Rumsfeld (search) said Tuesday, though he indicated it was unclear whether they were coming from elements of the Iranian government or from other parties.

"Weapons clearly, unambiguously from Iran have been found in Iraq," he told a Pentagon briefing. "It's a big border. It's notably unhelpful for the Iranians to allow weapons of those types to cross the border." He did not provide further specifics.

At the briefing, the Pentagon also announced that Iraqi and U.S. forces have arrested suspects in the deaths of 20 Marines in two incidents in Haditha, Iraq.

Air Force Gen. Richard Myers (search), chairman of the Joint Chiefs of Staff, pointed to the arrests as evidence that Iraqi civilians support the U.S.-led coalition trying to pacify the country.

"The public came forward and said these are the folks," Myers said. He did not say how many people had been detained or identify them but said those detained are being interrogated to determine their involvement.

Six Marine snipers were killed by small arms fire on Aug. 1. Last Wednesday, a Marine armored personnel carrier rolled over some land mines, which exploded and killed 14 Marines and a civilian translator.

Myers said the explosives that destroyed the carrier were in three stacked anti-tank mines buried just below the road surface.