Congressional sources confirmed late Thursday that a military transport plane carrying three Republican senators and a Democratic representative was attacked by either missiles or rocket-propelled grenades after taking off from the Baghdad airport.

Sens. Richard C. Shelby, R-Ala., James M. Inhofe, R-Okla., Mel Martinez, R-Fla., and Rep. Robert E. “Bud” Cramer, D-Ala., were uninjured after their C-130 transport plane took evasive measures and dispatched flares to avoid the incoming fire.

Shelby recounted the incident in a conference call with reporters. “I saw the red glare of a shell or a missile coming up toward our plane,” he said, “Then I saw a flare pop out and our plane just started moving and changing directions and trying to move.”

Laura Henderson, a spokeswoman for Shelby, confirmed the details of the attack and said the aircraft landed safely in Amman, Jordan. Henderson did not know whether the attack was being considered as random or if a specific security breach might have compromised the members’ safety.

Shelby praised the plane’s crew for successfully evading the attack. “We owe them,” he said.

A spokesperson for Multi-National Forces-Iraq said the military was still collecting information on the incident.

The attack comes at a time when both the Bush administration and Congress are collecting data on security conditions in Iraq in anticipation of resuming the debate over U.S. involvement next month.

Earlier Thursday, media reports said the Government Accountability Office would severely undercut administration claims that the security situation in Baghdad is stabilizing in a report due out next week.

And lawmakers from both parties are looking toward the upcoming testimony of Gen. David H. Petraeus, the top U.S. military commander in Iraq, and Ambassador Ryan Crocker to gauge whether or not the “surge” of troops in Iraq is achieving the positive results claimed by the administration.