The South Korean government has begun the process of verifying news reports that a South Korean teenager thought to have joined an Islamic militant group early this year was killed in a U.S.-led air strike in northern Syria, officials said Thursday.

“We are now trying to verify the facts with regard to the reports on his fate,” said a Seoul official on condition of anonymity.

A local media outlet reported Wednesday that the U.S.-led coalition forces carried out a massive air strike campaign last week in a stronghold of the Islamic State including a unit for foreign IS members that potentially included the 18-year-old Korean man, identified only by his surname Kim.

After leaving a note in which he expressed his wish to join the IS, Kim traveled to Istanbul, Turkey, in January. He later went missing there. In February, the IS released a video clip in which a man, presumably Kim, was seen engaging in military drills.

By Song Sang-ho (sshluck@heraldcorp.com)