Could Iran be plotting a Hizbollah offensive to take the heat off its leaders?

The house stands pulverised in the little valley behind Khirbet Silm, an unfinished two-storey villa that is now a grey mass of concrete rubble and dust, watched over by three sweating Lebanese soldiers.

The fires that raged here spread across a kilometre of hillside. But the explosions that started them have reverberated far further – to closed sessions of the UN Security Council, to the Israeli and Lebanese governments, to the Hizbollah, even to Iran.

Khirbet Silm, a Shia hill village sandwiched between tobacco fields and orange orchards has never been so famous – or infamous. Who would imagine that this heap of wreckage was a Hizbollah arms cache (illegally hidden inside the UN peacekeeping zone), a heap of shells and elderly rockets and small arms ammunition that spectacularly blew up this month? There were, according to the UN, 40 explosions in all that rippled across the valley, producing from an exceedingly uncomfortable Hizbollah a volley of highly unconvincing explanations.

Just old Israeli ammunition, it suggested, left behind from the Israeli-Hizbollah war of 2006? Hmm. Or, the Israelis left the ammunition there when they retreated in 2006. That's very definitely a "ho hum". Israel's hopelessly small 3,000-strong invasion force never reached within six miles of Khirbet Silm at that time. Which is why delegates to the UN in New York have been saying that the whole shebang was a clear breach of Resolution 1701, which clearly stipulates that no armed group may store ammunition between the Litani River and the "Blue Line" that effectively marks the Lebanese-Israeli border.

Four days after the explosions, on 18 July, UN peacekeeping troops and their Lebanese army colleagues gingerly moved in to inspect the site, at which point, "local villagers" started chucking stones at the French, Belgian and Italian blue hats, lightly wounding 14 of them.

According to the UN, some of these "villagers" were recognised as Hizbollah members, a view that was strengthened when groups of men were observed by the wreckage, heaping still-unexploded ammunition into wooden boxes for transportation out of the village. The shells and rockets they did leave behind turned out to date from the 1990s, but by then the whole affair had gone global.

The Israelis, still threatening to obliterate Iran's nuclear facilities, suspect that if they stage air strikes against the Islamic Republic, Hizbollah would open another war against northern Israel. Hence the outrage over this weapons cache. If you wish to strike at Iran, it seems, you must be able to do so with impunity; no second front from Lebanon.

In fact, the Iranians have long ago promised to exact a fearful toll on US troops in Afghanistan, Iraq and in the waters of the Gulf – let alone a nifty little strike on Israel's own nuclear base in the Negev desert – if Mr Netanyahu and his far-right Israeli government decide to attack. This is why Barack Obama has been flying out his top brass to Israel over the past few months. Netanyahu's threats are Washington's nightmare.

Worse still, Mahmoud Ahmadinejad's friends in Iran have been talking about the events in southern Lebanon. Is a new Hizbollah offensive being planned to take the heat off the crackpot President of Iran? And the Lebanese suspect that there's a far more dramatic dilemma forming between Obama and Netanyahu: that Netanyahu is threatening to let fly at Iran if Obama really forces him to end all Jewish colonisation in the West Bank.

The Lebanese live by conspiracies, but even the mayor of Khirbet Silm, Issam Majed, 47, an engineer, has an eloquent line by way of explanation. Sitting in the neatest, cleanest municipality building in all of southern Lebanon, this bespectacled bureaucrat declares: "When the Israelis fire at us with artillery or from the sea, the UN soldiers count the violations and that's it ... Then an explosion happens and it goes all the way to closed meetings of the UN Security Council in New York."

So why were those villagers suddenly throwing stones at the UN troops? "The UN arrived with tanks and armoured vehicles ... They flew helicopters all the time low over the village and frightened the women and children and the old people. Then they started to demand to enter people's homes. Foreign troops should not do this. Even the Lebanese army have to apply to the courts to do this."

Now this was a bit much. After 40 spectacular explosions inside its zone, the UN was highly unlikely to up sticks to the local judiciary in Tyre to ask for permission to hunt for armed men. And down at their base at Naqqoura, UN officials have all the right documentation for cynical reporters. According to its mandate, the UN soldiers "cannot search private houses unless there is credible evidence of a violation of Resolution 1701, including an imminent threat of hostile activity emanating from that specific location". So there you have it. The Israeli air force daily over-flies southern Lebanon – breaching, of course, Resolution 1701 and, presumably, looking for the arms hide-outs that no one finds – but the moment a house blows up at Khirbet Silm, you are going to have a Leopard tank at your front door.

Needless to say, poor old Major-General Claudio Graziani, the Italian UN commander, has got caught up in some familiar Lebanese spiders' webs. All he wants to do is help the innocent people of southern Lebanon, he opines. And – quite rightly – he holds a public meeting with local politicians, one of whom is the well-known elected Hizbollah MP, Hassan Fadlallah. The Israelis roar again: "Why is the UN negotiating with terrorists?" And so it continues.