KABUL, Jan. 30 (Xinhua) -- Taliban militants have claimed responsibility for killing three Americans who were killed in the so-called insider attack on Thursday night.

Zabihullah Mujahid, who claims to speak for the Taliban outfit in contact with media outlets on Friday, said that a Taliban infiltrator Ahsanullah of the eastern Laghman province "opened fire on American soldiers at Kabul airport killing three and injuring four others" on Thursday.

The attacker was also killed in firefight, Mujahid confirmed.

Meantime, U.S. officials, according to media reports have confirmed that four persons including three American contractors were killed in the military section of Kabul airport Thursday evening.

Afghan defense ministry Deputy Spokesman Daulat Waziri in talks with local media without giving details said that "investigation has been initiated into the case."