The raid took place early on Wednesday after the tribesmen repelled an attack near Qayyarah, a town about 60km (37 miles) south of IS-held city of Mosul.
It is not clear whether Iraqi or US-led coalition aircraft, which are flying sorties in the area, were responsible.
Mosul, Iraq's second largest city, has been under IS rule since June 2014.
But pro-government forces are planning to launch a major offensive to recapture it within weeks.
Qayyarah, which was recaptured in August, is seen as an important stepping stone in the build-up to the operation.
The commander of the Tribal Mobilisation in Nineveh (TMN) province, Sheikh Nazhan Sakhr al-Lihaybi, said his forces were regrouping after repelling an attack by IS militants east of Qayyarah when they came under fire from aircraft.
Agriculture Minister Falah Hassan Zaidan also confirmed that the strike took place, AFP news agency reported.
A TMN source told the BBC that he believed US-led coalition forces were responsible as they had been providing air support during the battle.
However, a spokesman for the coalition could not confirm if it had planes flying at the time of the attack, according to Reuters news agency.
The UN has said the humanitarian impact of the Mosul offensive could be "enormous", potentially affecting up to 1.2 million people.
At least 20 pro-government Sunni tribal fighters have been killed in an air strike in Iraq after being mistaken for Islamic State militants, sources say.