Israeli Prime Minister Benjamin Netanyahu heads the weekly cabinet meeting Sunday in his office in Jerusalem. (Uriel Sinai/GETTY IMAGES)

On this wind-swept hill overlooking Syria, Israeli soldiers are keeping a careful watch, scouring the landscape for signs of how the revolt against Syrian President Bashar al-Assad might affect the taut quiet along the frontier.

From the Israeli observation post, the adjacent Syrian villages of Bir Ajam and Bariqa looked deserted on a recent morning, weeks after they were the scene of fighting between Assad’s troops and rebels.

Some stray shells and bullets flew into Israeli-held territory during those clashes in November, drawing retaliatory fire that killed two Syrian soldiers. It was the first shooting across the cease-fire line since a disengagement accord was reached after the 1973 Arab-Israeli war.

Though calm has returned to the area for now, Israel has made contingency plans for what the upheaval in Syria could bring, particularly to the frontier on the Golan Heights, a strategic plateau captured from Syria in the 1967 Six-Day War.

Israeli officials say they have two main concerns should Assad be overthrown: that Syria’s stockpile of chemical weapons could fall into the hands of Islamist militants, such as the Iranian-backed Hezbollah group in Lebanon, and that a breakdown of security in Syria, particularly near the Golan frontier, could lead to militant attacks against Israeli targets across the cease-fire line.

In public remarks Sunday at the weekly meeting of his cabinet, Israeli Prime Minister Benjamin Netanyahu said that Israel is building a fence along the Golan line and that Syrian forces had pulled back from the frontier area, replaced by radical Islamist groups. Although those militants are for now battling the Syrian regime, Israeli officials are concerned that if Assad is ousted, the groups could turn their attention to Israel.

Netanyahu also expressed concern about Syria’s chemical weapons, saying that because “the Syrian regime is very unstable, the question of its chemical weapons worries us.” He said Israel was “coordinating our intelligence and assessments with the United States and others with the aim of being prepared for any scenario and possibilities that could develop there.”

Netanyahu met recently with Jordan’s King Abdullah II for discussions on Syria’s chemical weapons, according to a report last month in the London-based newspaper al-Quds al-Arabi. Israeli media said the meeting was confirmed by Israeli officials, though Netanyahu’s office declined to comment on the reports or on suggestions that Israel was weighing military action against the chemical arms stockpiles.

Moshe Yaalon, the Israeli minister for strategic affairs, said in an interview that Israel had warned Syria in recent months about the possible loss of control over its chemical arsenal.

“We conveyed a warning message that for us this is a red line, and then we indeed saw the Syrian regime organize to better protect these weapons, to concentrate them in a safer place and separate materials,” Yaalon said.

Amos Gilad, a top Israeli Defense Ministry official, recently told Israel Army Radio that Syria’s chemical weapons “are under control” for now.

Contingency plans for Golan

On the Golan front, Israeli officials are concerned that conditions there could follow a pattern that developed along Israel’s border with Egypt after the toppling of President Hosni Mubarak. A breakdown of security in Egypt’s Sinai Peninsula, where jihadist groups have gained a foothold, has led to cross-border shooting and rocket attacks on Israel, including an infiltration by gunmen that left eight Israelis dead in August 2011.

In his remarks Sunday, Netanyahu said that on the Syrian side of the Golan frontier, “the Syrian army has moved away, and in its place, global jihad forces have moved in.”

“Therefore, it is incumbent upon us to defend this border against both infiltration and terrorist elements, just as we are successfully doing on the Sinai border,” Netanyahu said.

Yaalon said Islamist militants, identifiable by their green Islamic banners, had taken over several Syrian villages in a buffer zone near Israeli lines, attacked Syrian army bases and assaulted a Syrian armored battalion. “Now they are directing their efforts against Assad, but it could be that after they get rid of him, they’ll turn their guns on us,” he said.

Touring the frontier during an earlier round of fighting near Israeli lines in July, Defense Minister Ehud Barak warned that “chaos” could develop after a possible overthrow of Assad and that “we could find the Golan Heights becoming a lawless area in which terrorist elements could also operate.”

On the ground, the Israeli army is preparing for what a military official called a worst-case scenario in which the long-quiet boundary with Syria would become “a hostile border.”

Trenches lined with coils of razor wire have been dug along the Israeli side of the Golan frontier, and a 15-foot-high steel fence is under construction, with plans to extend it to the length of the boundary with Syria. Surveillance of the Syrian side, aided by cameras, also is being stepped up.

Israel began beefing up barriers on the frontier after hundreds of protesters from Syria breached a boundary fence in May 2011, during rallies marking the anniversary of the establishment of Israel in 1948, marches that were repeated a month later on the anniversary of the 1967 war. Replacing a lower electronic warning fence, the imposing new barrier, encased in rolls of barbed wire, is intended to serve as a bulwark against infiltrators.

The fence is identical to one nearing completion along Israel’s border with Egypt, which runs from the southern edge of the Gaza Strip to the Red Sea resort of Eilat. That barrier was meant to stop illegal African migrants but is also seen as part of Israel’s defenses against cross-border attacks.

Risk of broader conflict

As the fighting in Syria spread to villages near the Israeli-held Golan in recent months, the Israeli military readied tents and medical supplies for the possible arrival of Syrian refugees. Barak warned that they would be stopped at the frontier.

But Syrian civilians fleeing the fighting did not head in that direction, taking shelter instead in areas outside their villages. Refugees in other border regions of Syria have crossed into Turkey, Jordan and Lebanon.

Despite occasional small-arms fire and shells from Syria hitting the Israeli-held Golan, there is no evidence to suggest that either Syrian forces or the rebels have an interest in opening another front, according to Israeli military assessments.

After the Israeli retaliatory fire in November, Syrian forces took measures to avoid overshooting into Israeli-held territory, the military official said, and the incidents were contained without escalating into broader conflict.

Still, the risk of wider hostilities remains. Limits imposed on the Syrian army’s forces and armaments in the buffer zone near the Golan make the area attractive for the rebels, who have been able to operate there without fear of Syrian airstrikes. When the Syrian army moved some tanks into the zone during the recent fighting, Israel objected, and U.N. observers in the area warned the Syrian side that it was violating the provisions of the disengagement accord.

In the one lethal exchange across the frontier in November, bullets struck an Israeli army patrol vehicle, causing no casualties. Israel fired back at a Syrian position with antitank missiles, and Syria said two of its soldiers were killed. The U.N. observers later reported that the Syrian army had blamed the initial shooting on the rebels, accusing them of trying to provoke the Israeli response.

The prospect of more spillover from the fighting in Syria could sharpen Israel’s dilemma: It wants to deter any more fire across the frontier that could cause Israeli casualties, but it does not want its response to set off broader clashes with Syrian forces.

“We don’t want to be dragged into the conflict, and we’re following a policy of restraint and containment,” the military official said. “If we would have a soldier or civilian killed, that would be a different story.”