Israel has Iranian-supported enemies in Lebanon to the north and Gaza to the south. Its back to the sea is safe. But security on its eastern border may be threatened if hostile Iran expands into an unstable Iraq.

Israeli analysts differ on the risk of encirclement by enemy forces allied to Tehran, on the degree to which Hamas and Hezbollah will do Iran's bidding, and on the chances of Iran gaining greater leverage in Baghdad via its Shi'ite connections.

They agree, however, that despite going to war in Lebanon in 2006 and Gaza in 2009, Israel has left powerful Iranian allies in place on these flanks. Of the two, the Hezbollah movement of Lebanon poses a more serious threat than Gaza's Hamas.

"I hope we'll have a quiet summer and things will get back on track," said Defence Minister Ehud Barak, after rocket attacks in the south, which he blamed on Hamas, and lethal fire in the far north with Lebanon's army which did not, according to Israeli statements, involve Hezbollah.

There is no sign that the incidents were linked. What they may portend is hard to gauge. Israel's greatest concern with Iran is, of course, to stop its suspected nuclear arms project. But the risk of border conflict may be more immediate. "It's impossible to predict when violence could occur," says Ephraim Kam of the Institute for National Security Studies. "The situation is volatile and violence could erupt any time."

Israel made peace with Egypt in 1979 and peace with eastern neighbour Jordan in 1994. Peace with a demilitarized Palestinian state in the West Bank would reinforce Israel's security, deepening its eastern buffer of non-hostile states.

There is a risk that violence overtakes diplomacy before a breakthrough can be achieved with the Palestinians. A war might raise Israeli security demands and Palestinian scepticism to a point that they scupper already remote prospects of a treaty.

A rocket strike from Gaza on the city of Ashkelon last Friday broke a year of calm there after a devastating Israeli offensive of Dec-Jan 2008-09 against Hamas.

A Gaza rocket on Saturday smashed into a children's centre in nearby Sderot. No one was injured in either strike. Israel's air force retaliated, killing a Hamas military commander in an attack on the Gaza Strip.

On Monday, a rocket salvo from the Egyptian Sinai overshot Israel's Red Sea resort of Eilat, killing a man in Jordan's Aqaba resort. It was "without a doubt" fired by Iranian-backed Hamas, said Israeli Prime Minister Benjamin Netanyahu, warning of harsh retaliation if repeated. Hamas issued a denial.

On Tuesday at the other end of the country, Lebanese gunfire -- from an army sniper by the Israeli account -- hit two Israeli officers as they watched a tree-pruning operation on the security fence below the U.N. "Blue Line".

Lebanon's army says it first fired warning shots, then Israelis fired at their soldiers, who shot back in turn.

An Israeli colonel died. Israeli artillery and tank fire then killed two Lebanese soldiers and a journalist. Both countries worked to keep the lid on after that. But it was the worst incident in four years of relative calm since the 2006 war.

"A thin line connects the rocket fire from Gaza on Ashkelon with the rocket fire from Sinai on Eilat and Aqaba, and runs all the way to the sniper's bullet that killed the commander," says a former Israeli National Security Council director, Uzi Dayan.

Israel must not leave security to others, he says. In talks with the Palestinians it must demand "sovereignty in all areas that are of vital security importance, first and foremost the Jordan Valley as Israel's eastern security border".

Israel's concern in the Jordan Valley, part of the Israeli-occupied West Bank captured by Israel in a 1967 war, is infiltration by Islamist guerrilla units and suicide bombers, rather than waves of tanks as in a conventional war of the past.

It is not yet clear how much of an obstacle this concern may be to securing an Israeli-Palestinian peace treaty.

Palestinian Authority President Mahmoud Abbas says the Jordan Valley must be part of a Palestinian state. Security provided by a third party such as NATO would be acceptable, he says, but not continued Israeli occupation there.

Iraq's inability to form a government seven years after the toppling of Saddam Hussein, and now the planned withdrawal of U.S. combat forces by the end of August, are not reassuring for Israel. But they do not necessarily mean Iran will profit.

"It's not true that Iran is surrounding Israel through proxies from all sides," said Kam. "Of course Iran is also gaining influence in Iraq. But you can't say that the moment the Americans pull out ... Iran will go in."

At this moment the compass of risk swings to Lebanon where, according to an Israeli military source, some Lebanese army units had "recently been very aggressive", threatening Israeli troops verbally and with gestures, and aiming their weapons.

While Israel held Lebanon responsible for the firefight, it did not suggest that Lebanese army chiefs instigated it, or that Hezbollah had infiltrated the Lebanese army to do so.

The incident was "an escalation because somebody made a mistake", said the military source, pointedly refusing to describe it as a deliberate attack.

Defence Minister Barak told Israel Radio it was a "provocation", but also declined to call it "an ambush".

"I don't think they planned this in the general staff of Lebanon. Nor do I think they planned it in Hezbollah. I don't know enough to tell you exactly who gave the order," he said.

Lebanon says Israeli forces had given notice about the tree-cutting to which they eventually agreed as long as it was U.N.-supervised. A senior U.N. peacekeeping official said Israel had rejected a UNIFIL request to supervise the operation.

Since the 1994 peace treaty, Jordan has blocked infiltration of Israel over the flat, open, desert Jordan Valley. And since its unilateral withdrawal from Gaza in 2005, Israel has kept the flat, open, desert Gaza Strip literally fenced in.

But the 120-km (75-mile) "Blue Line" of demarcation with Lebanon poses a stiffer challenge, jinking around steep, wooded valleys and mountain villages where Hezbollah can blend in, despite the presence of U.N. peacekeepers and the Lebanese army, which deployed along the border in late 2006.

UNIFIL says it has seen no transfer of weapons to the area.

"The Lebanese army is better than Hezbollah, and UNIFIL soldiers are better than the Lebanese army," Barak said.

"At the end of the day, none of them is perfect".