HASAKA, Syria — Forces from a Kurdish-led militia on rooftops traded fire with dozens of Islamic State fighters still holed up in an embattled prison in northeastern Syria on Thursday, despite claims by the U.S.-backed militia a day earlier that it had regained full control of the entire complex.
The prison, in the city of Hasaka, housed thousands of Islamic State fighters. Their fellow militants attacked a week ago in an attempt to free them. An official with one of the Syrian-Kurdish paramilitary groups battling ISIS said between 60 and 90 militants from the group were still fighting from inside the partly destroyed prison complex, most of them attackers who had stormed the prison but some of them prisoners who had joined forces with them.
The prison attack was the starkest evidence yet of a resurgence of ISIS across parts of Syria and Iraq, three years after the group lost the last territorial foothold in its so-called caliphate across a vast stretch of both countries. The extremists have also mounted a series of attacks on military forces in neighboring Iraq in recent months.
The prison fight drew the U.S. military into the fray in support of the Kurdish-led Syrian Democratic Forces, or S.D.F., providing airstrikes, intelligence and armored vehicles to cordon off the prison. This marked the broadest confrontation between American forces and ISIS since the end of the caliphate.
The fighting was also raging in surrounding areas near the prison complex.
At a traffic circle a few hundred yards from the prison complex in the center of Hasaka, a New York Times team took cover along with a group of local journalists and civilians caught in middle as Kurdish-led forces traded fire with ISIS gunmen who had opened fire from a street near the prison.
Explosions from rocket-propelled grenades fired by the Kurdish-led forces at the prison and the sound of truck-mounted antiaircraft guns rang out.
The S.D.F. said two ISIS fighters were killed in the engagement near the traffic circle but there were no reports of civilians harmed in that clash.
A bulldozer emerged from the ruins of a cultural center next to the prison complex carrying the crumpled body of an ISIS fighter before dumping it in the back of a pickup truck.
At another building behind the cultural center, which had been hit by an airstrike, S.D.F. fighters pulled out the remains of two other ISIS fighters. A charred oil tanker on its side still burned across the street.
Siyamend Ali, the head of media for the People’s Protection Units, one of the Kurdish factions in the S.D.F., said some of the ISIS militants still inside the prison were believed to be foreign fighters.
“The prison attack has activated sleeper cells in other places,” Mr. Ali said.
Sangar Khaleel contributed reporting.