A U.S. military transport helicopter crashed in bad weather in Iraq 's western desert Wednesday, killing 31 people, all believed to be Marines, while insurgents killed five other American troops in the deadliest day for U.S. forces since the Iraq war began.
Militants waging a campaign to derail Sunday's election carried out at least six car bombings and a flurry of other attacks on schools to be used as polling stations, political party offices and Kurdish sites, killing or wounding more than two dozen people.
While al-Qaida warned Iraqis to stay away from the polls — saying they would only have themselves to blame if they are hurt in attacks — President Bush called on people to "defy the terrorists" and cast ballots in the crucial election.
A Bush administration official said the cause of Wednesday's crash was not immediately known but that there was bad weather at the time.
The CH-53 Sea Stallion was carrying personnel from the 1st Marine Division when it went down about 1:20 a.m. near the town of Rutbah, about 220 miles west of Baghdad, while conducting security operations, the military said in a statement.
A search and rescue team has reached the site and an investigation into what caused the crash was under way.
The administration official said Wednesday that all 31 people killed in the crash were believed to be U.S. Marines — the most American servicemembers to die in a single incident in Iraq. It was also the deadliest day for U.S. forces since the March 2003 invasion.
Bush expressed his condolences for the deaths. "The story today is going to be very discouraging to the American people. I understand that. It is the long-term objective that is vital — that is to spread freedom," he told reporters.
He said "a lot of Iraqis" were expected to participate in the elections. "Clearly, there are some who are intimidated," Bush said. "I urge people to vote. I urge people to defy these terrorists."
In Iraq's Anbar province, four U.S. Marines were killed in fighting, the military said in a statement.
The statement gave no further details, but WABC reporter Jim Dolan, who was embedded with the troops who were attacked, said the deaths came when insurgents ambushed a Marine convoy leaving the town of Haditha, west of Baghdad, hitting a vehicle with a rocket-propelled grenade.
Also Wednesday, insurgents attacked a U.S. Army patrol near the northern town of Duluiyah, killing one soldier and wounding two others, the U.S. command said.
With the four Marines and the soldier's deaths, at least 1,377 members of the U.S. military have died in Iraq, according to an Associated Press count. If all 31 dead in the crash are confirmed to be military personnel, the count would rise to 1,408.
The previous single deadliest incident for U.S. troops was also a helicopter crash: In November 2004, two Black Hawk helicopters collided while trying to avoid ground fire, killing 17 servicemembers. Earlier that month, a Chinook transport helicopter was shot down by shoulder-fired anti-aircraft missile near Fallujah, killing 16 American soldiers and wounding 26.
The U.S. military has lost at least 33 helicopters since the start of the war, including at least 20 brought down by hostile fire, according to a study by the Brookings Institution.
Previously, the most Americans killed in one day came on March 23, 2003, when 26 troops were killed in various incidents during the U.S. military's drive to take Baghdad and topple Saddam Hussein. Bush declared major combat over on May 1, 2003, but fighting has continued.
Last month, a suicide bomb exploded at a mess tent in a base near Mosul, killing 22 people including 14 U.S. soldiers and three American contractors.
With only days before the election, guerrillas carried out a string of attacks Wednesday targeting political groups and voting sites.
A suicide bomber detonated a vehicle packed with explosives at the offices of the Kurdistan Democratic Party in the town of Sinjar, just outside Mosul, killing or wounding at least 20 people, said KDP official Mahdi al-Harki.
Earlier in the day, gunmen opened fire with machine guns on the local headquarters of the Patriotic Union of Kurdistan and the Communist Party in the city of Baqouba, north of Baghdad, killing a traffic policeman. The KDP and PUK are the two largest Kurdish groups in Iraq and have formed a coalition along with other Kurdish groups to run in the election.
Insurgents set off three car bombs in rapid succession in the town of Riyadh, north of Baghdad, killing at least five people — including three policemen.
Four American soldiers were injured in a car bombing Wednesday in Saddam Hussein's hometown of Tikrit, the U.S. command said. Another car bomb targeted a multinational forces convoy on the road to Baghdad's international airport, injuring four soldiers, the command said.
The attack temporarily closed the airport road, one of the country's most dangerous. Up to four mortar shells exploded Wednesday near a police station in the northern Baghdad suburb of Sabaa al-Bor, injuring at least one Iraqi.
A Web site statement, purportedly from al-Qaida in Iraq, said it carried out the attack on the airport road, claiming that the targets were Americans.
The group also warned Iraqis to stay away from the polls Sunday. It said the Americans were organizing "fraudulent elections" and that Iraqi troops were protecting "the Jews and the Christians."
"The enemies of God will see that death is their destiny and failure their ally," the group said. "Oh people, be careful. Be careful not to be near the centers of infidelity and vice, the polling centers ... Don't blame us but blame yourselves" if harmed." The statement's authenticity could not be verified.
In new attacks, two schools slated to be used as polling stations were bombed overnight. A ground floor classroom in one of the buildings, a preparatory school for girls, was littered with broken glass and its main entrance was blackened and clogged with debris.
Al-Arabiya television broadcast a videotape showing three men identified by insurgents as election workers who were kidnapped in Mosul. The satellite station said the three were abducted by the Nineveh Mujahedeen, which threatened to attack polling stations on election day.
U.S. troops and insurgents also clashed in the city of Ramadi, west of Baghdad, in fighting that doctors said killed on Iraqi.
Iraqis will choose a 275-member National Assembly and regional legislatures. Sunni Muslim extremists have threatened to sabotage the election and many Sunni clerics have called for a boycott because of the presence of 170,000 U.S. and other foreign troops.
In Baghdad's Sadr City district, Iraqi forces backed by U.S. troops raided a Shiite mosque, detaining up to 25 followers of a radical cleric Muqtada al-Sadr, police and the cleric's supporters said.