The United Nations says Israeli construction along a demilitarised buffer zone with Syria has led to “severe violations” of a 50-year-old ceasefire agreement, which risk increasing tensions along their shared frontier in the occupied Golan Heights.
Satellite photographs show new trenches and earth berms dug over the past few months along the length of what is known as the Area of Separation (AoS).
The BBC has filmed construction taking place alongside a military vehicle near the town of Majdal Shams, and fresh earthworks in rural land further south. The work in both locations is believed to lie within Israeli-controlled areas.
The UN Disengagement Observer Force (UNDOF) says most of the Israeli construction does not breach the AoS, but that some trenches – dug under protection from military vehicles including tanks – do cross into it, and that Israeli army vehicles and personnel have also entered the buffer zone.
Beneath the watchtower at UNDOF’s Camp Ziouani base, the Israeli fence snakes towards a line of volcanic mountains; a Syrian flag flutters in the trees beyond the post, marking the other side of the separation zone.
UNDOF observers monitor the 80km (50-mile) long strip of land 24 hours a day.
Chief of Mission Bernard Lee told the BBC that two major lines of trenches had been dug, along with three more limited ones, each some 6m (20 ft) wide.
He estimated that trenches crossed into the AoS in a handful locations, by a couple of metres in each case, but said he had not visited the sites himself.
UNDOF was not able to immediately share visual evidence of the reported incursions, and permission for the BBC to view or film the locations from a nearby observation post has so far not been granted.
Initial searches of satellite photographs have not produced images in enough detail to independently confirm the UN allegations.
The AoS was set up as part of Israel’s ceasefire agreement with Syria in 1974, following Israel’s earlier occupation of the Golan Heights.
Israeli forces are required to be west of the so-called Alpha Line, while Syrian forces must be east of the Bravo Line, which runs along the other side of the AoS.
Israel unilaterally annexed the Golan in 1981. The move was not recognised internationally, although the US did so unilaterally in 2019.
Israeli settlers there live alongside about 20,000 Syrians, most of them Druze, who stayed on in the Golan after it was captured.
Despite the presence of Iran-backed militia groups in Syria, this frontier has remained relatively calm, as Israeli ground forces have battled Iranian allies in Gaza and Lebanon over the past 13 months.
But UNDOF said in a statement that the Syrian authorities had “strongly protested” the ongoing Israeli work. And that the UN itself had “repeatedly” taken its concerns over the Israeli violations to Israel’s military authorities.
Israeli Defence Forces (IDF) spokesman Lt Col Nadav Shoshani told the BBC that the trenches were designed to protect against infiltration by Iran-backed groups in Syria – and did not break the ceasefire agreement.
“Israeli officials have been communicating with the UN about these issues,” he said. “And I can tell you that the IDF is operating on Israeli territory making sure that a terror invasion is not possible, making sure we are defending our borders.”
The threat of a surprise invasion by Israel’s neighbours has loomed larger here since the 7 October Hamas attacks.
“Will [the trenches] stop what happened on 7 October? Yes,” said Bernard Lee. “Could you get a pick-up truck over it? No.”
But the defences being built along this frontier don’t address the more immediate threat from drones and missiles regularly launched by Iranian militia groups in Syria and Iraq – and frequently shot down by Israeli forces.
Nor do they address Israel’s concerns about Syria being an “oxygen line” for Iran to smuggle weapons to its Lebanese ally, Hezbollah.
Mr Lee said commercial smugglers already used the AoS to smuggle cigarettes and electronics between Syria and Lebanon. And that a new patrol road, built by the UN, is assisting them.
“They come over the mountain, enter the area of separation with a trail of pack horses, eight at a time, with two armed guys,” he said. “They unload the pack horses and a pick-up truck meets them at our road: we’ve motorized the smuggling business.”
Asked whether the same route could be used to take weapons from Syria into Lebanon, he replied: “That is what the IDF are concerned about.”
Israel has also pointed to what it says are “daily” violations along the demilitarized frontier by Syria.
In May, Israel’s ambassador to the UN wrote to the secretary-general to complain about Syrian violations, including “armed presence in the area of separation” which “only heighten tensions in our already volatile region”.
Iran-backed militia in the area are a concern for Syrian President Bashar al-Assad’s regime, too, after years of civil war.
It has appeared unwilling to be drawn in to the Israel-Hezbollah war, despite frequent Israeli strikes inside Syria targeting Hezbollah and Iranian positions and weapons shipments.
“The situation is frightening,” said Wafik Farhat, a Syrian hotel owner in the occupied Golan Heights. “Our eyes are looking more to the sky than to the plants. There’s fear here.”
Farhat’s eco-lodge, with its yurt accommodation surrounded by orchards, looks out onto rows of fresh trenches along the buffer zone.
“It gives us a sense of security,” he said. “We can sleep in peace, because there’s someone taking care of the border and not letting terrorists cross towards us.”
Israel is already fighting Iranian allies – Hamas and Hezbollah – on two of its borders. But more than a year into this regional conflict, friction is also being felt along its quietest frontier.
