Violent chaos has engulfed northeastern Syria amid a Turkish invasion after President Donald Trump ordered US troops out of the region and away from Kurdish allies that have fought alongside US forces for years.

The New York Times reported that after Trump's decision, American military forces were unable to complete a transfer of "about five dozen 'high value' Islamic State detainees."

According to the Times, hundreds of Islamic State sympathizers were also able to escape a low-security detention camp in the region as Kurdish forces guarding the facility pivoted to fend off the Turkish attack.

Last week, Trump claimed that the US had moved some of the "most dangerous" ISIS prisoners in Syria but did not provide further details.

A US official told CNN earlier Sunday that the chaos on the ground in Syria means the US campaign to defeat ISIS in the country is "over for now," and that the US policy in the region "has failed."

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Violent chaos topped off the fifth day of a Turkish invasion in northeastern Syria after President Donald Trump ordered US troops out of the region and away from Kurdish allies that have been fighting alongside the US for years.

American military forces could not transfer "about five dozen 'high value' Islamic State detainees" out of Kurdish-run facilities before the withdrawal was announced, two American officials told The New York Times.

Last week, Trump claimed that the US had moved some of the "most dangerous" ISIS prisoners in Syria but did not provide further details.

"We're putting them in different locations where it's secure," he said. It is unclear how many prisoners Trump was referring to or where those prisoners were being placed.

Officials told the Times that only two British detainees from the cell known as "The Beatles" were taken into US custody.

According to the Times, hundreds of Islamic State sympathizers were also able to escape a low-security detention camp in the region as Kurdish forces guarding the facility pivoted to fend off the Turkish attack, marking a concerning shift in the region.

One camp in Ain Issa, a town located in the former ISIS stronghold of Raqqa just 20 miles from the Turkish border, was left completely unguarded on Sunday as Turkish forces pounded Kurdish positions with airstrikes and ground advances, an administrator of the camp told the Times.

Read more: Disaster is unfolding in Syria as videos emerge of US allies being slaughtered and hundreds of ISIS prisoners escape during airstrikes

US Defense Secretary Mark Esper said on Sunday that the remaining 1,000 US troops in northern Syria would be withdrawn, but US officials told The Daily Beast they will just be moved further away from the advancing Turkish forces. A Turkish airstrike nearly hit a small group of US soldiers stationed in Syria on Friday.

Observers have noted that the US withdrawal may pave the way for an ISIS resurgence in the region. A US official told CNN on Sunday that the chaos on the ground in Syria means the US campaign to defeat the Islamic State in the country is "over for now," as ISIS was revived and "with nearly 100,000 [people] who will rejoin their jihad."

The official said, in their opinion, that "US policy has failed."

Turkish President Recep Tayyip Erdogan has turned hawkish as the US has retreated, overseeing key military captures along the border that have taken some Kurdish control.

Trump on Sunday night claimed again that the US had taken custody of "the worst of the ISIS prisoners."

"Turkey and the Kurds must not let them escape. Europe should have taken them back after numerous requests. They should do it now. They will never come to, or be allowed in, the United States!" he said in a tweet.

Kat Tenbarge contributed to this report.