BAGHDAD (Reuters) - Bomb blasts and rocket and mortar fire killed 38 people as Iraqis voted on Sunday in an election they hoped would distance their nascent democracy from years of sectarian slaughter as U.S. troops pack up to leave.
The explosions rumbled across Baghdad and other cities after Sunni Islamist insurgents vowed to wreck voting for Iraq's second full-term parliament since the 2003 U.S. invasion, a vote watched closely by global oil companies planning to invest billions to develop the country's dilapidated oilfields.
Turnout among the 19 million eligible voters was not clear.
It could take three days to get results in an election that will prove vital to President Barack Obama's plan to halve U.S. troop levels by August and withdraw completely by end-2011.
"I have great respect for the millions of Iraqis who refused to be deterred by acts of violence, and who exercised their right to vote today," Obama said in a statement. "Their participation demonstrates that the Iraqi people have chosen to shape their future through the political process."
There were immediate signs the results could be contested.
Iyad Allawi, head of a secular coalition and a top candidate for prime minister, criticised confusion at voting centres. An alliance of the two main parties in Iraq's semi-autonomous Kurdish region said thousands of Kurds were excluded because their names could not be found on voter rolls.
"We feel this is politically motivated and we demand a clarification and solution. If that does not happen we will not accept the election result," said a statement from the Patriotic Union of Kurdistan and the Kurdistan Democratic Party.
Iraqi authorities said dozens of mortar and rocket attacks rattled Baghdad during the early hours of polling, although Defense Secretary Robert Gates said 80 percent of the explosions heard in the capital were believed to be noise bombs.
In the deadliest incident, 25 people were killed when an explosion destroyed a three-storey Baghdad apartment block. Rescuers pulled bodies from the rubble as a woman buried under debris screamed to be saved.
"It is terrible that lives have been lost, but it doesn't change the course of the Iraqis," said Ad Melkert, the U.N. special representative to Iraq. "There will be issues, but they are serious elections and many Iraqis have participated with great conviction."
Iraq's Independent High Electoral Commission said only two polling stations had to be closed briefly for security reasons.
The Islamic State of Iraq, an al Qaeda affiliate, had warned Iraqis not to vote and vowed to attack those who defied them.
The 96,000 U.S. troops still in Iraq stayed in the background, underscoring the waning American role in Iraq, but U.S. helicopter gunships provided aerial support.
ISLAMIST OR SECULAR
Voters in the ethnically and religiously divided country were given a choice between Shi'ite Islamist parties that have dominated Iraq since Saddam Hussein's fall and secular rivals.
Prime Minister Nuri al-Maliki, a Shi'ite, urged all parties to accept the results and called militants' attacks a disgrace.
"They cannot see democracy and freedom," he said. "All their challenges have failed and the population will win."
Allawi, one of Maliki's opponents, had already complained of irregularities in early voting and on election night he criticized the electoral commission (IHEC) for "wide and severe confusion" at voting centres.
"I ask the next parliament to open a full investigation in the issue of election and the roles played by some government officials, also to include all the IHEC members," he said.
Allawi's secular alliance is tapping into exasperation with years of conflict, poor public services and corruption, and hopes to gain support from the once privileged Sunni minority that views Maliki's Shi'ite-led government with suspicion.
There were few signs of a repeat of the Sunni boycott of a 2005 election that left them on the fringes of Iraqi politics and fueled an insurgency that killed thousands. But some Sunnis were skeptical that the election would improve their lot.
"They blamed us because we did not vote last time. I came with my wife to vote although I am not enthusiastic, because I know there will be no change," said Mohammed Abode, 37, who cast his vote at a center in Ramadi, in Sunni Anbar province.
About 6,200 candidates from 86 factions are vying for 325 parliamentary seats. No bloc is expected to win a majority, and it may take months to form a government, risking a vacuum that armed groups such as Iraq's al Qaeda offshoot might exploit.
Few elections in the Middle East have been as competitive as this one. Its conduct could determine how democracy in Iraq affects a region used to kings and presidents-for-life.
Maliki, whose State of Law coalition is claiming credit for improved security since sectarian warfare peaked in 2006-07, also faces a challenge from former Shi'ite allies, derided by Sunni militants as pawns of neighboring Iran.
Anti-American Shi'ite cleric Moqtada al-Sadr, speaking at a rare news conference in Tehran, said holding an election under the "shadow of occupation" was illegitimate, but urged Iraqis to vote anyway to pave the way for "liberation" from U.S. forces.
Sadr galvanized anti-U.S. sentiment after the 2003 invasion but faded from the political scene after vanishing, ostensibly to embrace religious studies in Iran, more than two years ago.
(Additional reporting by Saif Tawfeeq, Aseel Kami, Khalid al-Ansary and Rania El Gamal in Baghdad, Waleed Ibrahim in Ramadi, Mohammed Abbas and Khaled Farhan in Najaf, Mustafa Mahmoud in Kirkuk, Ayla Jean Yackley in Arbil, Muhanad Mohammed in Basra and Sabah al-Bazee in Tikrit; Writing by Alistair Lyon and Jim Loney; Editing by Michael Christie and Ralph Boulton)