warplane
© Reuters
An airstrike has left at least 20 pro-government tribal fighters dead near the Iraqi city of Mosul, a US defense official told AFP, while admitting that the strike had "most likely" been carried out by US-led coalition jets.

At least 20 pro-government militia members were killed on Wednesday in the Qayyara region just 60 kilometers from the key Iraqi city of Mosul, according to media reports. Local police have confirmed the attack, which happened around 1 am local time (22:00 GMT on Tuesday).

"This most likely was from a coalition air strike. Right now, we are still getting information,"a US senior defense official told AFP, adding that, while an investigation has been launched, it was presumed that the strike had been "what we unfortunately call a blue-on-green incident," meaning it was likely a mistake.

According to Canadian Brigadier-General David Anderson the US-led coalition and Iraqi military are currently investigating the incident near Mosul.

"We are aware of the alleged reports that coalition forces mistakenly fired on Sunni tribal fighters," Anderson said during a news briefing on Wednesday. "We are looking into this to determine the facts that surround the case," he added.

Local tribesmen had accused the US-led coalition of carrying out the strike earlier.

"The [US-led] coalition aircraft attacked the positions of tribal militia fighters in Qayyara region, resulting in the death of 21 soldiers and injuries to five more," a representative for the militia was quoted by Al Sumaria news agency as saying.

He also called on Washington and Iraqi officials to swiftly launch an investigation into the case. Iraq's agriculture minister, Falah Hassan Zaidan, confirmed the information, saying that 21 tribal fighters had been killed in the strike, AFP reports.

The group, which is led by tribal leader Sheikh Nazhan Sakhr al-Lihaybi, had reportedly just finished successfully repelling an IS attack when it was bombed.

Mosul has been held by Islamic State (IS, formerly ISIS/ISIL) since 2014.

It is the group's most crucial outpost in Iraq. The militia that came under attack is reported to be one of the pro-government forces operating against jihadists in the area.

A major offensive to drive IS militants out of Mosul could start as early as this month, according to the Iraqi and US militaries. In December of 2015, dozens of Iraqi troops were killed and injured when their positions were hit by US jets in Iraq's Anbar province.

Following that incident, US Defense Secretary Ashton Carter called Iraqi Premier Minister Haider al-Abadi to express his condolences.

A similar incident occurred in the neighboring war-ravaged Syria on September 17, when US-led fighter jets attacked positions of the Syrian government forces near the town of Deir ez-Zor, killing 62 soldiers.While Washington called the case a "mistake" Damascus said that the incident was "blatant aggression."