The UN force, UNDOF, confirmed its personnel observed "unidentified armed individuals in the area of separation, including approximately 20 who went into one of the mission's positions in the northern part of the area of separation", a spokesperson for UN Peacekeeping told AFP.

"The inviolability of UN premises must be respected at all times."

Meanwhile, the Israeli army said "an attack was carried out by armed individuals at a UN post in the Hader area in Syria," the army said in a statement, referring to a Syrian town on the edge of the buffer zone.

"The (Israeli army) is currently assisting the UN forces in repelling the attack."

Late on Saturday, Israeli Foreign Minister Gideon Saar posted on X: "During the last day, armed forces entered the buffer zone on the Syrian side of the border with Israel. Among other things, attacks were carried out on the (peacekeepers) in the area".

He said Israel was "troubled by violations" of the 1974 armistice with Syria. "Israel does not intervene in the internal conflict in Syria," he added.

Earlier on Saturday, Syrian rebels took control of the provincial capital of Quneitra around 12 kilometres (eight miles) south of Hader, Britain-based war monitor the Syrian Observatory for Human Rights said.

The long-stalemated Syrian civil war burst back into life late last month, with rebels sweeping across the country and capturing multiple major cities.

The military said army chief Herzi Halevi visited the Syrian border on Saturday. He too underlined that Israel was not intervening in Syria.

He said Israel's "primary focus is on observing Iran's movements and interests" while a "secondary focus" was on Syrian factions and "ensuring they do not mistakenly direct their actions towards us".

The military declined to comment on Saturday evening when asked if the attack was ongoing.

Israel conquered most of the Golan Heights during the Six-Day War of 1967 and later annexed the territory in a move never recognised by the international community as a whole.

UNDOF has patrolled a buffer zone between the Israeli- and Syrian-controlled zones since 1974.

In August 2014, Islamist rebels attacked UNDOF and took more than 40 Fijian peacekeepers hostage, holding them captive for almost two weeks.