The aid group did not identify the aircraft in the attack Sunday in an area of fighting between the Kenyan government and the Islamic militant organization al-Shabaab, The New York Times reported.
Officials in Kenya confirmed an airstrike in the area but said it hit an al-Shabaab training camp, not a humanitarian site. They said 10 militants were killed and 47 injured.
"We hit an al-Shabaab camp. Five hundred meters [about 546 yards] from that camp is an internally displaced-persons camp," Kenyan military spokesman Maj. Emmanuel Chirchir said.
The militants were responding to the strike when a vehicle armed with an anti-aircraft gun was hit and errantly drove into the humanitarian camp, Chirchir said.
"It was already burning, and because of all the ammunition it exploded," Chirchir said.
Kenya has blamed al-Shabaab for a rash of kidnappings of Westerners from Kenya. Kenyan troops, tanks and gunships crossed the border into Somalia last month.