NEW YORK — A 16-year-old American boy fighting on behalf of the Islamic State was captured on the battlefield in Syria, an American-backed force fighting the militants said Wednesday.
If the teenager is proved to be a United States citizen, he would be the first American minor to be caught fighting on behalf of the terrorist group overseas.
His arrest follows the capture of Warren Christopher Clark, 34, a former substitute teacher from Texas whose seizure in the same area was announced on Sunday. They are among the handful of American citizens — just five so far — who have been taken alive on the front line in the battle against the Islamic State, according to a database maintained by the Program on Extremism at George Washington University.
The militia that announced the boy’s capture, the Syrian Democratic Forces, said he was among eight foreign fighters who were apprehended this week in the last sliver of Islamic State-held territory in northeastern Syria. The others included citizens of Germany, Russia, Ukraine, Tajikistan, Kazakhstan and Uzbekistan.
United States officials did not immediately respond to a request for comment, and over the weekend the same militia announced the capture of what they said was another American citizen. There were indications, however, that that person might be from Trinidad, according to Simon Cottee, a senior lecturer in criminology at the University of Kent.
Mr. Cottee also said that he had a name very similar to that of the teenager said to be American in a database kept to track Islamic State fighters from Trinidad.
The captures were announced three weeks after President Trump declared “We have won against ISIS,” another name for the Islamic State, and ordered the withdrawal of 2,000 American troops from Syria.
While United States officials have estimated that 295 Americans either have joined or tried to join militant groups in Iraq and Syria, they have not said how many of those recruits successfully made it to the battle zone, nor which group they joined.
The database maintained by the Program on Extremism has identified just 55 American nationals who joined the Islamic State. That is a small fraction of the number from countries like France, from where at least 1,400 people are believed to have joined, according to the Paris-based Center for the Analysis of Terrorism.
While the 16-year-old would be the only American minor caught on the battlefield, other American teenagers have been found in Islamic State-controlled territory.
A 15-year-old girl from Kansas was repatriated from Syria, after being forced to travel to the war zone by her father. She was forcibly married to an ISIS fighter and was pregnant at the time of her capture.
And several other American teenagers have been arrested for trying to carry out attacks on behalf of the militants in the United States. Prosecuting them has proved difficult because of their age, said Seamus Hughes, the deputy director of the George Washington University Program on Extremism.
In South Carolina, for instance, Zakaryia Abdin was accused of plotting an attack against soldiers on behalf of the Islamic State at age 16. He initially pleaded guilty to a firearms offense and was sentenced to one year in a juvenile facility. Only when he tried to travel to Syria following his parole, then age 18, did the Justice Department charge him with providing material support to a foreign terrorist organization.
In New Jersey, Santos Colon, 17, pleaded guilty in 2017 to participating in a plot to kill Pope Francis during a Mass in Philadelphia two years earlier. He was released to a halfway house pending sentencing; he faces up to 15 years in prison.
“Here’s the concern with this case,” Mr. Hughes said, referring to the teenager apprehended in Syria. “How long has this young man been in Syria? Did he go early on with family? Or is it a more recent case of traveling? And he is purported to have been fighting for ISIS. It’s one thing to say it and another to prove it in a court of law, and authorities may well decide not to prosecute him given his age.”