AKCAKALE, Turkey — Hundreds of relatives of Islamic State fighters fled a Kurdish-run detention camp on Sunday morning after Turkish airstrikes hit the surrounding area, deepening the crisis prompted by the Turkish-led invasion of northern Syria.
The escapes came hours before the United States military said it would withdraw its remaining troops from northern Syria in the coming weeks, despite a likely resurgence of the Islamic State amid chaotic efforts by Turkish-led troops to wrest the region from Kurdish control.
A Kurdish official also said that the flag of the Islamic State, also known as ISIS, had been raised in the countryside between the camp in the Kurdish-held town of Ain Issa and the Turkish border, another indication of how the Kurdish authorities were losing control of a region they had freed from the extremists only months ago.
“We are facing very fierce attacks and we’re forced to decrease numbers of guards,” said the official, Ciya Kurd, of the Kurdish-led regional authority, who confirmed the break from the displacement camp after the Turkish strikes.
Defense Secretary Mark Esper announced in an interview with CBS’s “Face the Nation” broadcast on Sunday that the United States would be evacuating about 1,000 American troops from northern Syria in a “deliberate withdrawal.”
He said that the United States found itself “likely caught between two opposing advancing armies” in northern Syria, and called the escalation of the conflict in the region a “very terrible situation.”
The defense chief added that the United States had learned that Turkey was likely to expand its incursion “farther south than originally planned and to the west” in Syria, according to a transcript of his remarks published by CBS.
The Kurdish authorities are in negotiations with the Syrian and Russian governments to form an alliance against the Turkish force, Mr. Esper said, adding that the United States did not want to be caught in the crossfire.
The Kurdish authorities are “looking to cut a deal, if you will, with the Syrians and the Russians to counterattack against the Turks in the north,” Mr. Esper said.
President Trump has declared ISIS defeated, but his decision to pull back American troops shielding Kurdish allies in northern Syria could result in the group’s resurgence and has already had devastating consequences for the Kurds. They lost thousands of fighters in the battle against the extremists and are now fighting a war on two fronts.
A video capturing the execution on Saturday of at least two Kurdish prisoners by Turkish-backed Syrian Arab fighters illustrated the fallout of the invasion.
On Sunday, American troops stationed in Ain Issa withdrew from the town as Turkish-led forces moved closer to its perimeter, a United States military official said, even as relatives of ISIS fighters mounted an escape from the detention facility elsewhere in the town.
The retreat came as Turkey’s airstrikes pummeled Ain Issa, about 20 miles south of the Turkish-Syrian border, causing panic and unrest in a camp that housed nearly 13,000 displaced people, fewer than 10 percent of whom were relatives of Islamic State fighters.
Scores of people, including more than 700 relatives of ISIS, fled the camp, according to the Kurdish authorities. The number could not be independently verified, but a witness confirmed by phone that he had seen crowds of people hurrying from the camp around 9:30 a.m. Sunday.
The humanitarian aid group Save the Children also confirmed that foreign nationals had left the camp. Sonia Khush, who oversees the group’s work in Syria, citing her colleagues at the camp, said that a secure facility that housed ISIS relatives was now empty.
“What was not clear to us was whether some of the women and children were taken by coalition forces or whether they all managed to escape,” Ms. Khush said. “It seems to be a mix of the two. Some women and children may be in the main camp.”
The Kurdish authorities had repeatedly warned that, while they were confronted by the Turkish invasion, they would not have the resources to secure the prisons and camps containing ISIS fighters and their relatives.
After establishing a foothold on Saturday in Ras al-Ain, a strategic town close to the Turkish border, Turkish troops and their Arab proxies made major progress on the ground on Sunday. A Syrian Arab militia under Turkish command pushed deeper into Kurdish-held territory, blocking major roads, ambushing civilians and claiming the capture of a second strategic town in northern Syria, Tel Abyad, that lies adjacent to the border.
President Recep Tayyip Erdogan of Turkey announced that his forces now controlled nearly 70 square miles of territory in northern Syria. They have also taken control of the most important highway that connects the two flanks of Kurdish-held territory, the Turkish defense ministry said. This allows Turkish troops and their proxies to block supply lines between Kurdish forces.
Mr. Erdogan also suggested his campaign was now expanding in scope. He announced that the Turkish force would attempt to capture Al Hasaka, a major Kurdish-run city that sits well beyond the territory that Mr. Erdogan initially said he had set out to capture.
Turkey and its Syrian Arab allies are trying to wrest control of northern Syria from a Kurdish-led militia that spearheaded American-backed operations against the Islamic State and that is the offshoot of a Kurdish guerrilla group based in Turkey.
Since the Syrian civil war began eight years ago, northern Syria has changed hands several times, as secular rebels, Islamist rebels, extremist groups and Kurdish factions have vied with government forces for control.
After partnering with American troops to drive out the Islamic State, the Kurdish-led militia emerged as the dominant force across the area, enraging and frightening the Turkish authorities, who see the group, which calls itself the Syrian Democratic Forces, as a terrorist organization.
On Sunday morning, Turkish-backed Arab militias ambushed and captured four employees of the Kurdish Red Crescent, a medical aid group, traveling north from Ain Issa toward the besieged town of Tel Abyad, a member of the aid group said by phone. The four employees were in a two-car convoy.
The Turkish-led force also took control of Suluk, an Arab town about five miles inside Kurdish-held territory, according to the Turkish state-run news agency Anadolu. A Syrian activist in touch with the combatants and civilians in the area, Mustafa Hamida, confirmed the news.
Close-fire fighting could be heard in Tel Abyad on Sunday morning from the Turkish border town of Akcakale, suggesting that Turkish forces had entered the town after a four-day siege. The two adjoining towns are separated by customs buildings and a cement border wall.
Turkish-backed Arab fighters posted photos on an online chat room of combatants standing in front of a security building in a western neighborhood of the town, and Turkish television footage showed Arab fighters within the town’s perimeter.
The invasion has caused a huge surge in displacement, with more than 130,000 people fleeing their homes since fighting began on Wednesday. Many had already been displaced during the Syrian conflict.
Carlotta Gall reported from Akcakale, Turkey, and Patrick Kingsley from Istanbul. Ben Hubbard contributed reporting from Dohuk, Iraq, Eric Schmitt from Washington, Hwaida Saad from Beirut, Lebanon, and Iliana Magra from London.