The conflicting death counts came at a time when Iraqi officials are under increasing pressure to stop attacks. Last week, angry Iraqis in Baghdad hurled stones at police and soldiers because they failed to stop a car bombing.
The suicide attacker wore an Iraqi military uniform in Thursday's bombing - the fourth major attack on Iraqi security forces in a week. That raised troubling questions about insurgents' ability to infiltrate the country's armed forces or to receive help from inside their ranks.
U.S. officials have based their hopes for Iraq's future on building a professional Iraqi military capable of securing the country as the U.S. draws down its forces this year.
Two Iraqi army officers, contacted by telephone from Baghdad, said the bomber detonated an explosive belt among soldiers headed for a canteen at Habbaniyah air base in Anbar province 45 miles west of Baghdad.
One of the officers described a "thunderous" explosion that left "bodies and pieces of human flesh scattered all over near the canteen." He said 16 soldiers were killed and 50 wounded. The second officer said only that a number of soldiers had died.
Both officers spoke on condition of anonymity because they were not supposed to release information to media.
Later, however, the Defense Ministry spokesman, Maj. Gen. Mohammed al-Askari, said 38 Iraqi soldiers were wounded but only the bomber died. Maj. Gen. Mardhi Mishhin al-Mahalawi, the army's Anbar operations chief, said 17 soldiers were wounded.
The sprawling base was sealed off and reporters were unable to enter to check on the conflicting reports. U.S. troops are also based at Habbaniyah, but the U.S. military referred all questions about casualties to the Iraqis. There was no indication of any U.S. casualties.
An American who identified himself as a soldier training Iraqis at the base telephoned The Associated Press to say he witnessed the attack but would not give his name.
The caller said the soldiers had finished a morning training session and were walking to the canteen for lunch when the bomber, who was waiting for them on the street, detonated his explosives.
He said only the bomber was killed but 38 others were injured. About half were treated and released, he said.
But police Maj. Mohammed al-Dulaimi, who works at a station near the base, said he saw saw at least 10 mangled bodies removed from the blast site to a local hospital. He said the Iraqi military refused to give local police any casualty figures.
In nearby Fallujah, a mosque loudspeaker announced the name of a soldier said to have been killed in the blast. It was unclear whether he could have been the bomber.
No group claimed responsibility for the blast, but suicide bombings are the signature attack of al Qaeda in Iraq, which was active in Anbar until Sunni tribesmen turned against the terror movement in 2006 and joined forces with the Americans.
At least 37 people have been killed in four major attacks on Iraqi security forces since April 10, when a suicide truck bomber blasted the regional police headquarters in Mosul. Five American soldiers and two Iraqi policemen were killed in the Mosul blast.
In addition, 11 Oil Ministry guards were killed and 13 wounded in a car bombing in Kirkuk on Wednesday. Nine government-backed Sunni paramilitaries died and 30 were wounded in a suicide bombing Saturday at an army base south of Baghdad.
Prime Minister Nouri al-Maliki has based much of his political legitimacy on the fact that the country has calmed during his stewardship. Renewed attacks are likely to threaten his position politically.
In Washington, Defense Department spokesman Bryan Whitman said Thursday that the latest bombings show "there is still the ability to conduct these spectacular and lethal attacks."
The recent attacks have raised questions whether Iraqi forces are capable of providing security when U.S. troops withdraw from Baghdad and other cities by June 30 - the deadline set in the U.S.-Iraqi security agreement that took effect this year.
President Barack Obama has also promised to end the U.S. combat role in Iraq by September 2010 and withdraw all American forces from the country by 2012.
Last week, however, the top U.S. commander, Gen. Raymond Odierno, told The Times of London he is concerned that Iraqi forces won't be ready to assume full responsibility for Mosul, Iraq's third largest city, by the June deadline.
Odierno said al-Maliki would face a "very difficult" political decision whether to ask U.S. troops to stay longer in Mosul, where al Qaeda and other Sunni insurgents still operate.
However, an Iraqi military spokesman told reporters Thursday that there has been no change in the plan for American soldiers to leave Mosul, Baghdad and other cities on schedule.
"There are withdrawal timetables in the security agreement," Maj. Gen. Qassim al-Moussawi said. "The first stage of the withdrawal will be from all cities by June 30."
Two Sunni lawmakers Thursday criticized Odierno for suggesting that the Americans might have to stay longer in Mosul.
Noureddin al-Hayali described Odierno's comments as a "violation of the pullout accord." Lawmaker Hashim al-Tae urged the prime minister to raise a new army division from among Mosul's population, adding that "our citizens reject the stationing of foreign forces" in the city.