BAGHDAD — A suicide bomber ripped through a line of anti-al-Qaida Sunni fighters waiting to collect their paychecks near an Iraqi military base as nearly 50 people were killed in violence west of Baghdad.

The attack is the deadliest this year against the groups that turned against the terror network amid an apparent campaign by insurgents to undermine confidence in the government security forces and their allies.

The attacks on the Awakening Council members highlighted the daunting security challenges the country faces as the U.S. works to withdraw all combat troops in Iraq.

The first attack Sunday morning by a single bomber with an explosive vest killed at least 45 people and wounded more than 40 at a checkpoint near a military base in the mostly Sunni district of Radwaniya southwest of Baghdad.

Some 150 Sunni fighters had lined up to collect their paychecks when the bomber struck, according to witnesses.

"I ran, thinking that I was a dead man," said Uday Khamis, 24, speaking outside the Mahmoudiyah hospital where many of the wounded were taken. His left hand was bandaged and his clothes were stained with blood.

At least a dozen men, dressed in military-style uniforms were seen laying in pools of blood in front of a blast wall in footage obtained by the Associated Press Television shortly after the blast.

There were conflicting reports as to how many of the dead were Iraqi soldiers and whether accountants who were killed as they were handing out money were civilian or military.

In the second attack, a suspected militant stormed into a local Awakening Council headquarters in the far western town of Qaim near the Syrian border and opened fire on those inside.

The town and the vast desert province of Anbar, were for years the epicenter of the Sunni Arab insurgency and a sanctuary for al-Qaida.

The fighters returned fire, wounding the attacker, who then blew himself up as they gathered around him, killing three and wounding six others, police officials said on condition of anonymity.

All officials spoke on condition of anonymity because they were not authorized to speak to the media.

Two other members of the Sunni militia were also wounded in other minor attacks south of Baghdad.

While violence has dropped dramatically over the past two years in the country, Iraqi security forces remain a favorite target for insurgents bent on destabilizing the country and its Shiite-led government.

The attack also raised to the surface the festering resentment on the part of some Awakening Council members toward a government they said has largely marginalized them, even though their decision to fight alongside the Americans has made them targets for Sunni extremists.

The complaints take on greater urgency given Iraq's current political stalemate and the scheduled withdrawal of all U.S. combat forces by the end of August.

More than four months after March's inconclusive parliamentary election, Iraq has yet to form a new government as politicians bicker over who will lead the country. The impasse has raised fears that militants will try to exploit the political vacuum to re-ignite sectarian tensions that brought Iraq to the brink of civil war in 2006 and 2007.

While the Awakening Councils played a key role in reducing the overall level of violence in Iraq, their future role in the Shiite-dominated government is uncertain.

The U.S. used to pay the monthly salaries of about $300 to the nearly 100,000-strong militias. Last year, the Iraqi government took over paying their salaries and, after heavy pressure from the Americans, agreed to absorb up to 20 percent of the fighters into its security forces, while giving the others government jobs.

"The government has not provided job opportunities to the heroes who fought al-Qaida," Sheik Efan Saadoun, a member of the provincial council in Anbar said. "Therefore, these heroes are not willing to fight al-Qaida because they have not received what they deserved."

Others appeared to imply that the government was at least complicit in the attacks Sunday.

Khamis, the bombing victim, said while men are usually searched at the checkpoint where the bomber struck, on Sunday they were allowed to line up without any checks.

Hassan Ali, who was waiting at the hospital with his wounded nephew, said also this was the fifth day they had gone to the base to try and collect their paychecks.

"Every time they went to receive their salary, they told them to come the next day and they did that for four days and now in the fifth day this explosion took place," he said.

Associated Press Writer Bushra Juhi contributed from Baghdad.