Israel’s prime minister has announced its military has temporarily seized control of a demilitarized buffer zone in the Golan Heights, saying the 1974 disengagement agreement with Syria had “collapsed” with the rebel takeover of the country.

Benjamin Netanyahu said he had ordered the Israel Defense Forces (IDF) to enter the buffer zone and “commanding positions nearby” from the Israeli-occupied part of the Golan.

“We will not allow any hostile force to establish itself on our border,” he said.

A UK-based war monitor said Syrian troops had left their positions in Quneitra province, part of which lies inside the buffer zone, on Saturday.

On Sunday, the IDF told residents of five Syrian villages inside the zone to stay in their homes until further notice.

The Golan Heights is a rocky plateau about 60km (40 miles) south-west of Damascus.

Israel seized the Golan from Syria in the closing stages of the 1967 Six-Day War and unilaterally annexed it in 1981. The move was not recognised internationally, although the US did so unilaterally in 2019.

The Israeli move in the buffer zone came after Syrian rebel fighters captured the capital, Damascus, and toppled Bashar al-Assad’s regime. He and his father had been in power in the country since 1971.

Forces led by the Islamist opposition group Hayat Tahrir al-Sham (HTS) entered Damascus in the early hours of Sunday morning, before appearing on state television to declare Syria to now be “free”.

Netanyahu said the collapse of the Assad regime was a “historic day in the Middle East”.

“The collapse of the Assad regime, the tyranny in Damascus, offers great opportunity but also is fraught with significant dangers,” he said.

He said events in Syria had been the result of Israeli strikes against Iran and the Iran-backed Lebanese armed group Hezbollah, Assad’s allies, and insisted Israel would “send a hand of peace” to Syrians who wanted to live in peace with Israel.

The IDF seizure of Syrian positions in the buffer zone was a “temporary defensive position until a suitable arrangement is found”, he said.

“If we can establish neighbourly relations and peaceful relations with the new forces emerging in Syria, that’s our desire. But if we do not, we will do whatever it takes to defend the State of Israel and the border of Israel,” he said.

After more than a year of war in the Middle East, Israel already has its hands full.

But the pace of events in Syria, it’s northern neighbour, will be of real concern.

The IDF had already moved reinforcements to the occupied Golan.

In normal times, its warning to residents in several villages to stay in their homes because Israel would not hesitate to act if it felt it needed to would be seen as hugely provocative and enough to start a war.

Israel is especially concerned about who might get their hands on Bashar al-Assad’s alleged arsenal of chemical weapons.

The leader of the Syrian rebellion is Abu Mohammed al-Jawlani. His family roots are in the occupied Golan Heights, where thousands of Israeli settlers now live alongside about 20,000 Syrians, most of them Druze, who stayed on after it was captured.

Israel will have no intention of giving that land up and is determined to protect its citizens.

During the 2011 Syrian uprising, Israel made the calculation that Assad, despite being an ally of both Iran and Hezbollah, was a better bet than what might follow his regime.

Israel will now be trying to calculate what comes next in Syria. Like everyone, it can only guess.

• What is the occupied Golan Heights?