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An injured girl is transported to a makeshift hospital after what activists said were at least 20 air strikes on February 5, 2015. In a first move of its kind, US military has admitted two children were killed during air strikes against Isis in Syria.Mohammed Badra/Reuters

In a first move of its kind, the US military has admitted to killing innocent civilians amidst the US-led air strikes against the Islamic State (Isis) militant group in Syria.

US military confirmed on Thursday (21 May) that two civilian children were victims to the air strikes.

Lieutenant General James L Terry who directed the investigations and is heading the US-led coalition against IS said in a statement, reported AFP News: "We regret the unintentional loss of lives.

"The coalition continues to take all reasonable measures during the targeting process to mitigate risks to non-combatants, and to comply with the principles of the Law of Armed Conflict."

Despite the US Department of Defence allegedly conducting a, "thorough assessment, review, and validation process of the targeted buildings" before the 5 to 6 November 2014 air strikes on the Khorasan Group, they found, "no indication that there were children at any of the targeted buildings".

"The preponderance of the evidence in the investigation indicates the airstrikes conducted against facilities used by Khorasan Group in the vicinity of Harim City, Syria, likely led to the deaths of two non-combatant children," read a news release by the US Central Command on Thursday (21 May).

"Measures were taken to avoid unintended death or injury of non-combatants during the strike by reviewing the targets thoroughly prior to engagement, relying on accurate assessments of the targets, and engaging the targets when the risk to non-combatants was minimised."

The Khorasan Group is an al-Qaeda offshoot operating in Syria.

In 2014, news emerged that the Khorasan group is allegedly trying to broker a merger between IS and Jabhat al-Nusra, the Syrian branch of al-Qaeda.

"Khorasan sees its role now as securing an end to the internal conflict between Islamic State and al Nusra," said a senior rebel source, according to a Daily Beast report.

The three groups involved in the merger talks, included, Khorasan, IS and al-Nusra, all of which were a part of al-Qaeda originally.