Two U.S. helicopters collided while landing at a base in Baghdad on Saturday, killing one Iraqi soldier and wounding four people, including two Americans, the military said, the second helicopter crash in two weeks.
The U.S. military said hostile fire did not appear to be the cause.
Also Saturday, the military said it killed an al-Qaida in Iraq leader suspected of masterminding one of the deadliest attacks in Baghdad as well as recent bombings and the 2006 videotaped killing of a Russian official.
The two UH-60 Black Hawks crashed shortly before 9 p.m. in a northern section of the capital known as Azamiyah, the military said. The wounded included two American troops and two other Iraqis, but the total number of people on board was not yet known, a statement said.
"The situation is under control. Emergency services are on the scene," military spokesman Lt. Patrick Evans said. An investigation into the crash was under way.
Two Iraqi police officials, speaking on condition of anonymity because they weren't authorized to release the information, said the crash occurred during clashes between gunmen and U.S.-backed Iraqi forces in northern Baghdad.
Evans denied the reports, saying "we have absolutely no reports of any clashes taking place nearby."
A witness who identified himself only by his nickname Abu Sattar said he was receiving guests in his house when he heard a big explosion.
"We went outside the house and we saw a fire coming from nearby. Then we heard the sounds of gunfire and U.S. soldiers came and sealed off the area," he said.
The U.S. military relies heavily on helicopters to ferry troops, dignitaries and supplies to avoid the threat of ambushes and roadside bombs. At least 70 U.S. helicopters have gone down since the war started in March 2003, according to military figures. Of those, 36 were confirmed to have been shot down.
On Sept. 18, a CH-47 Chinook en route from Kuwait crashed in the southern desert about 60 miles west of Basra on Sept. 18, killing all seven American soldiers on board. The military said that crash apparently was due to a mechanical problem, not hostile fire.
The al-Qaida in Iraq leader was killed Friday elsewhere in northern Baghdad. American troops also killed the man's wife in a firefight as they tried to capture him, the military said.
Mahir Ahmad Mahmud al-Zubaydi, also known as Abu Assad or Abu Rami, was accused of directing an insurgent cell believed to be responsible for nearly simultaneous car bomb and suicide attacks Thursday, according to the statement.
Iraqi police and hospital officials have said some two dozen people were killed in Thursday's attacks targeting two Shiite mosques in Baghdad.
Those attacks and others that struck during Ramadan have raised fears that al-Qaida in Iraq is trying to provoke Sunni-Shiite reprisal killings as U.S.-led forces begin to draw down.
Al-Zubaydi was among the most senior insurgents killed by U.S. forces as they seek to shore up security gains that have driven the level of violence to its lowest point in more than four years.
Gen. Ray Odierno, the top U.S. commander in Iraq, said Shiites were "showing very much restraint" and authorities "haven't seen any signs" that they plan to retaliate.
"I think we've made some good inroads inside of the network that was doing this," he told reporters after a ceremony in Diwaniyah marking the departure of Polish troops from Iraq. "I feel confident that we will continue to go after them and make it very difficult for them to continue."
Al-Zubaydi's death will be a major blow to al-Qaida in Iraq even as the group's recruiting efforts have been "severely curbed" by a decision by many Sunnis to join forces with the Americans in the fight against it, military spokesman Rear Adm. Patrick Driscoll said.
The military also blamed al-Zubaydi for several car bombings and mortar attacks in Baghdad's main Shiite district of Sadr City in 2006 and 2007, including a series of blasts that killed more than 200 people on Nov. 23, 2006 — one of the deadliest attacks to strike the Iraqi capital.
Al-Zubaydi also was believed to have planned and participated in abductions and videotaped executions, including one in which he was seen shooting one of four kidnapped Russians, according to the statement.
The Russian embassy workers were abducted in June 2006 after an attack on their car in Baghdad's Mansour neighborhood. They were later killed, along with a fifth Russian.
Meanwhile, Deputy Secretary of State John Negroponte and the U.S. Ambassador to Iraq Ryan Crocker met with Iraq's president and other officials Saturday in northern Iraq in an apparent bid to step up pressure to reach agreement on a joint security deal, Iraqi officials said.
They traveled to the Kurdish city of Sulaimaniyah and the disputed city of Kirkuk, which is at the center of a power struggle between the Kurds and Arabs.
The agreement is due to replace a U.N. mandate for foreign forces in Iraq that expires on Dec. 31, but the talks have hit an impasse over Iraqi demands for increased jurisdiction over U.S. troops in Iraq.
The U.S. Embassy confirmed that Negroponte was meeting with Iraqi officials in the north but provided no details.