The four-decade-old U.N. peacekeeping operation in the Golan Heights region between Israel and Syria, largely curtailed last week because of Syria’s civil war, was further undermined Tuesday with confirmation that the Philippines contingent was going home.

President Benigno S. Aquino III of the Philippines, in an interview with The New York Times while attending the U.N. Climate Summit, said that most of the Filipino soldiers, having retreated from the buffer zone between Israel and Syria to the Israeli side last week because of Syrian insurgent attacks, had departed for the Philippines.

Aquino has grown increasingly exasperated with the Golan peacekeeping operation, known as the U.N. Disengagement Observer Force, or UNDOF, which is ill equipped to deal with heavily armed Syrian insurgents.

The peacekeepers have not been permitted to significantly strengthen their own arsenal despite recurrent threats of kidnapping and attack. A group of Filipino soldiers was abducted in March 2013 by one Syrian rebel faction, and last month two outposts staffed by Filipinos came under insurgent assault.

It was unclear when, or even whether, the Filipino forces would be replaced in the UNDOF operation, which also includes troops from Fiji, India, Nepal, Ireland and the Netherlands, some of them also subjected to attacks from the Syrian side.

Forty-five Fijian soldiers were abducted last month by the Nusra Front, an affiliate of al-Qaida, but released unharmed Sept. 11 after two weeks.

A U.N. Department of Peacekeeping Operations official, who spoke on the condition of anonymity because the issue is politically delicate, said that the Philippines had long signaled its intention to withdraw from UNDOF, and that after its soldiers were attacked in August, "a decision was made to advance their planned repatriation."

The absence of an international presence in the area of separation, created after the 1973 Arab-Israeli war, has added new instability to the frontier between Israel and Syria, which technically remain in a state of war.

That instability was reinforced Tuesday when Israel said it had shot down a Syrian fighter jet over the Israeli-controlled Golan that the Israelis contended had strayed into their airspace. It was the first time in at least a quarter-century that the Israelis had downed a Syrian warplane.

Israel has responded on several occasions in the past three years to what it has described as errant fire from the Syrian civil war. In August, Israel shot down a Syrian drone.

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