"When our forces arrived, they found cases of collective escapes due to the camp having been opened up in a haphazard manner," interior ministry spokesman Noureddine al-Baba told a news conference.

Al-Hol, the largest camp for relatives of suspected IS jihadists in northeastern Syria, had been under the control of the Kurdish-led Syrian Democratic Forces (SDF).

But last month, Syrian troops drove Kurdish forces from swathes of the north, sparking questions over the fate of the IS prisoners and their families.

Under pressure, the SDF withdrew from the camp on January 20, with Syrian security forces taking control a few hours later.

"The SDF withdrew suddenly, without coordination and without informing" the Syrian authorities or the international anti-jihadist coalition beforehand, al-Baba said.

There was a "chaotic situation" after the Kurdish forces pulled out, he added, and "more than 138 breaches" have been discovered in the camp's 17-kilometre (11-mile) perimeter wall that allowed mass escapes.

After the Kurdish forces withdrew, thousands of women and children fled the camp to parts unknown.

The SDF said in a statement that "the withdrawal of our forces was a direct result of the military attack... targeting the camp and its surroundings by forces affiliated with Damascus".

The release of IS families "occurred after the entry of Damascus-affiliated factions (into the camp) and involved their direct participation", it added.

Al-Hol housed 23,500 people, mostly Syrian and Iraqis, the ministry spokesman said.

Around 6,500 foreigners of 44 different nationalities lived in a high-security section of the camp.

Last week, Syrian authorities moved the families still at Al-Hol to another site in the country's north.

Before the Kurdish forces withdrew, the United States military had transferred more than 5,700 detained IS suspects from Syrian prisons to Iraq.

The US had previously announced it would transfer around 7,000 detainees.

IS swept across Syria and Iraq in 2014, committing massacres and forcing women and girls into sexual slavery.

Backed by US-led forces, Iraq proclaimed the defeat of IS in the country in 2017, and the SDF ultimately beat back the group in Syria two years later.

The SDF went on to jail thousands of suspected jihadists and detain tens of thousands of their relatives in camps.