RAQQA, Syria — Hours after the expiration of a four-day truce between Syrian government forces and Kurdish-led fighters Saturday, Syria’s Defense Ministry announced the ceasefire had been extended by 15 days.

The ministry said in a statement that the extension was in support of an operation by U.S. forces to transfer accused Islamic State militants who had been held in prisons in northeastern Syria to detention centers in Iraq.

The Kurdish-led Syrian Democratic Forces, or SDF, confirmed the ceasefire extension.

“Our forces affirm their commitment to the agreement and their dedication to respecting it, which contributes to de-escalation, the protection of civilians, and the creation of the necessary conditions for stability,” the group said in a statement.

Over the last three weeks, there have been intense clashes between government forces and the SDF, in which the SDF lost large parts of the area they once controlled.

Earlier in the day, the Kurdish-led force called on the international community to prevent escalation.

The end of the truce came as government forces had been sending reinforcements to Syria’s northeast.

Syria’s interim government signed an agreement last March with the SDF for it to hand over territory and to eventually merge its fighters with government forces. In early January, a new round of talks failed to make progress over the merger, leading to renewed fighting between the two sides.

A new version of the accord was signed last weekend, and a four-day ceasefire was declared Tuesday. Part of the new deal is that SDF members will have to merge into the army and police forces as individuals.

The SDF said in a statement Saturday that military buildups and logistical movements by government forces had been observed, “clearly indicating an intent to escalate and push the region toward a new confrontation.” The SDF said it would continue to abide by the truce.

State TV said authorities on Saturday released 126 teenage boys who were held at the Al-Aqtan prison near the northern city of Raqqa that was taken by government forces Friday. The teens, all under 18 years of age, were taken to Raqqa where they were handed over to their families, the TV station said.

The prison is also home to some of the 9,000 members of the Islamic State militant group who are held in northeastern Syria. Most of them remain held in jails run by the SDF. Government forces have so far taken control of two prisons, while the rest are still run by the SDF.

Earlier this week, the U.S. military said that some 7,000 Islamic State detainees would be transferred to detention centers in neighboring Iraq. On Wednesday, the U.S. military said that 150 prisoners had been taken to Iraq.

Alsayed writes for the Associated Press.