The deaths last Friday took place when celebratory gunfire by insurgents prompted warplanes to act, believing they were doing so in self-defence, Nato chief of allied operations Brigadier General Mark van Uhm said.
There was no formal investigation into the incident.
Van Uhm refused to say what type of aircraft were involved in the incident or what country they were from.
The air raid killed 13 people, four of them civilians, some 15 kilometres east of the battleground Libyan oil town of Brega, according to the rebels.
"We have noted that the opposition forces have already stated that it was their fault, that there had been some celebratory fire in the air, which led to the reaction," Uhm said.
The rebels have "learned their lesson" by moving "those very enthusiastic young people away from the frontline" and sending more experienced fighters to replace them, he said.
The insurgents were expected to start exporting on Wednesday, after a Liberian-flagged tanker docked at the eastern port of Tobruk on Tuesday, according to Michelle Bockmann of Lloyds List.
The tanker is reported to be able to load one million barrels of oil, worth 70.5 million euros.
The rebels would neither confirm or deny the report that the ship was due, because forces loyal to Moamer Kadhafi were trying to bomb the Mislah oilfield.