NATO forces accidentally struck a convoy of five cars belonging to rebel forces west of Ajdabiyah today, reportedly killing at least 15 Libyan rebels and injuring seven.
A plane enforcing the international no-fly zone hit the rebel vehicles, including an ambulance, between Brega and Ajdabiyah when an anti-aircraft gun was fired into the air, the BBC reported.
The accidental hit was a result of NATO forces, who are aiding Libyan civilians, confusing forces loyal to strongman Moammar Ghadafi and rebel groups. Forces on both sides are using civilian vehicles and not wearing uniforms, while most are wearing civilian clothing, according to rebel forces.
NATO officials said they are aware of the reports of the attack and are investigating, according to the BBC.
Representatives of the rebels have told ABC News correspondents that rebels they are not angered by the incident. They say they understand that collateral damage is to be expected and that they want NATO to keep up the pressure on Ghadafi.
"As regrettable as it may be, we understand that we might have to give up lives for the greater good. We have to look at the bigger picture," opposition spokesman Mustafa Gheriani told The Associated Press. "This is a war and the lines are so fluid going back and forth, so it's natural that mistakes will happen."
Another opposition spokesman, Abdel-Hafidh Ghoga, told the AP the incident was an example of the rebels' lack of coordination, which has hindered them in their fight against Gadhafi's troops.
"This unfortunate accident was a mistake that was caused by the rebels' advance during the coalition's attack," Ghoga said. "Now the military leadership that has been organized more effectively recently is working on preventing the recurrence of these accidents."
The accident today, however, was the second in two days. Seven civilians were killed Friday near Brega, including three sisters, according to the BBC. A doctor interviewed in the area told the BBC that despite the casualties he wants the airstrikes to continue.
Aside from allegations that have been made by Ghadafi's regime, these are the first reports of civilian casualties resulting from NATO airstrikes since the beginning of the enforcement of the no-fly zone.
Since the beginning of the NATO operations on March 31, a total of 363 sorties and 148 strike sorties have been conducted.
A strike sortie means that the mission was available to drop weapons, but didn't necessarily do so.
Doubts About NATO in Libya as U.S. Takes Backseat
With the U.S. pledge to shift the majority of combat actions to Britain, France and other NATO allies, there is hope that a barrage of assaults on Gadhafi's strongholds will bolster the disjointed rebel forces after several days during which they have lost much of the ground they gained in the first days of the strikes.
A number of U.S. combat forces will cease operations on Sunday, including U.S. Navy destroyers and submarines that have been launching Tomahawk cruise missiles from the Mediterranean. Also beginning Sunday no U.S. aircraft will be flying strike missions -- though planes and naval vessels will be on standby.
Military experts said that America's reduced role in enforcing the Libyan no-fly zone could cripple efforts to keep Gadhafi's forces from battering the rag-tag army trying to topple him.
They said they fear that without U.S. willingness to go after Gadhafi's troops and equipment from the air, and without U.S. ground controllers pinpointing targets, the effort to shield the rebels will fail.
"The idea that the AC-130s and the A-10s and American air power is grounded unless the place goes to hell is just so unnerving that I can't express it adequately," said Sen. Lindsay Graham, R-S.C. "The only thing I would ask is, please reconsider that."
Even Defense Secretary Robert Gates wondered out loud whether the NATO airstrikes can succeed without the United States in the lead.
"They certainly have made that commitment, and we will see," Gates said.
NATO announced today that in the last 24 hours, it flew 174 sorties, including 74 that were strike sorties. The other flights were surveillance or refueling flights.
Officials said Gadhafi's army has lost as much as 25 percent of its firepower, but it still outnumbers the Libyan opposition by 10-to-1.