REUTERS - Israel's frontier with Syria, where militants have kidnapped 45 UN peacekeepers, has become a magnet for Islamist activity and Israel itself is now a target, the defense minister and security analysts said on Tuesday.

The Nusra Front, an al-Qaida-linked group fighting Syrian President Bashar Assad, has established a major presence in the region, analysts said, and is poised to carry out attacks across the barren borderlands where Syria, Israel and Jordan converge.

Iran meanwhile is seeking to expand its influence in the region via its support for Assad and the Lebanese militant group Hezbollah, all of which are allied against the Sunni insurgency confronting Assad, Israeli Defense Minister Moshe Ya'alon said.

"Iran's fingerprints can be seen in Syria, including in the Golan Heights, in attempts to use terror squads against us," Ya'alon told an economic conference as he set out the combined threat from Islamist groups in Syria.

In their latest assault, Nusra Front fighters seized 45 Fijians serving as UN monitors in the demilitarized zone on the Golan Heights between Israel and Syria. It is demanding to be removed from global terrorism lists in exchange for their release.

"We now have Jabhat al-Nusra, which is basically al Qaida, on the border with Israel, and Israel is a legitimate target for Muslim militants all over," said Aviv Oreg, a retired Israeli intelligence officer and a specialist on al Qaeda.

Oreg said it was only "a matter of time" before the Islamist groups now engaged in fighting in Syria turn more of their attention towards Israel.

"I cannot tell you exactly when, but it's very risky. It only needs one suicide bomber to cross the fence and attack an Israeli military patrol or a tractor full of farmers going to work in the fields..."

But while Israel may be growing alarmed, it is not clear that the Jewish state is a strategic priority for Nusra or other radical Sunni Muslim groups.

Their focus since 2011 has been the overthrow of Assad, a campaign that has bogged down from infighting in their ranks and Shi'ite Muslim Hezbollah's intervention on the side of Assad.

If Israel is attacked in any serious way, the retaliation would likely be intense, setting back the insurgency and opening the way for Assad's forces to further reclaim the initiative.

Israel has bolstered its forces in the Golan Heights, a rugged plateau seized from Syria during the 1967 war, with armored patrols keeping a close eye across the frontier, sometimes passing within 300 meters (yards) of Nusra fighters.

The plateau, scattered with fruit farms, vineyards and rocky peaks, looks down across the plains of southwest Syria, where Nusra and other groups, including the secular, Western-backed rebel Free Syrian Army, can be seen battling Assad's forces.

After three years of fighting, opposition forces control patches of territory to the west and south of Damascus, including a portion of the 375-km (225-mile) border with Jordan.

That has allowed thousands of foreign fighters from both the Arab world and Europe to cross into Syria, including an estimated 2,000 Jordanians. At least 10 Israeli Arabs have also gone to Syria, five of whom were later detained after returning home, according to Oreg.

Risky corner

The frontier between Israel and Syria has been administered by the United Nations since 1974, a year after the last war between them. It consists of an area of separation, a narrow strip of land running about 70 km (45 miles) from Mount Hermon on the Lebanese border to the Yarmouk River with Jordan.

About 1,200 soldiers are involved in monitoring the separation zone, in what has been for most of the past 40 years one of the world's quietest peacekeeping missions. That changed with the uprising against Assad, and the area is now precarious.

Stephane Cohen, the former chief liaison between the Israeli army and the UN peacekeeping force known as UNDOF, said the UN's mandate was now meaningless.

With the Philippines, Ireland and other contributing nations set to withdraw from the mission, it was questionable whether the United Nations could continue monitoring the area.

"UNDOF is collapsing and the mandate has not been relevant for at least two years," said Cohen, now a defense analyst with the Israel Project, a pro-Israel advocacy group.

"Eighty percent of the border area is now in the hands of (Syrian) opposition forces," he said, adding that if more nations withdrew, the militant presence would only rise.

For now, Israel is merely remaining vigilant.

"We have to be very cautious about our retaliation policy," said Oreg, emphasizing that the priority should be to keep careful tabs on the Nusra Front and other groups' capabilities, while sharing any intelligence judiciously.

