Yesterday marked the fifth day of artillery clashes along the Syrian-Turkish border, amid rising fears that the fighting could trigger a war that would spread across the Middle East.

On Sunday another apparently stray shell from Syria landed in the Turkish border town of Akçakale near a plant belonging to the Turkish Grain Board. There were no casualties and only minor damage to the building. The Turkish military responded by firing artillery rounds back into Syria.

The US is backing the Turkish government and Syrian opposition forces as part of its continuing proxy war to oust Syrian President Bashar al-Assad. The latest shelling came as the opposition, which is largely supplied and supported from Turkey, intensified attacks on Syrian army forces near the Turkish border. On Saturday Syrian “rebel” forces captured the village of Jisr al-Shughur after attacking a Syrian army post there.

The exchange of artillery fire between Syrian and Turkish army forces on Saturday occurred after two Syrian mortar shells reportedly landed near the village of Guveççi. Turkey responded by shelling Syrian military positions. No one was hurt in Turkey, however.

Guveççi lies about 10 miles from Darkoush in Syria, where Syrian opposition forces were attacking army positions and both sides were exchanging mortar fire. At least seven injured Syrian opposition fighters were taken to Turkey for medical treatment.

The exchange of artillery fire between the Turkish and Syrian armies began Wednesday when mortar fire from Syria killed five Turkish civilians in of Akçakale. The Turkish army responded by launching air strikes on a Syrian military camp near Tal Abyad town, which reportedly killed three Syrian soldiers.

The Russian government, an ally of the Syrian regime, said it had received assurances from Damascus that the Syrian mortar fire that landed was an accident. Turkish broadcaster NTV reported that Syria had ordered its warplanes and artillery units not to go within six miles of the Turkish border.

Turkish Prime Minister Recep Tayyip Erdogan reportedly dismissed Moscow’s assurances, however. A Turkish official said that the mortar fire Wednesday was “of a different magnitude” than previous cases where fire from Syria fell inside Turkey.

The US and Turkish governments are responding by provocatively threatening Syria with war. This comes after nearly a year during which the US has unsuccessfully sought to obtain permission from the United Nations Security Council to launch military operations, such as a no-fly zone, to back Syrian opposition forces against the government.

Over the weekend, US Defense Secretary Leon Panetta indicated that the fighting between Syria and Turkey could “escalate,” implicitly threatening that Turkey could launch a broader assault against Syria. Since Turkey is a NATO member state, it could also try to invoke treaty provisions that would force other NATO member states in Europe and North America to enter the war on its side against Syria.

Speaking at a military summit in Paraguay, Panetta said: “Whether or not that conflict begins to extend into the neighboring countries such as Turkey remains to be seen. But obviously the fact that there are now exchanges fired between these two countries raises additional concerns that this conflict could broaden.”

Panetta also threatened Syria’s main regional ally, Iran, even as crippling US and European sanctions directed at its oil industry create price inflation and protests inside Iran. If Iran did not satisfy US concerns about Iran’s nuclear program, he warned, “Make no mistake, the international community will continue to impose additional sanctions.”

Panetta’s comments came only two days after Turkey’s Islamist Justice and Development Party (AKP) government passed legislation giving Erdogan powers to send soldiers into “foreign countries.” Turkey’s air force and navy were subsequently put on full alert. (See also: Mass protest against threatened Turkey-Syria war)

The legislation prompted mass protests in Istanbul. There were also antiwar protests in border regions of Turkey near Syria.

The border clashes underscore that the US-backed rebellion in Syria has escalated into a regional proxy war that threatens to involve the entire Middle East or the entire world.

Iran, which has a security treaty with Syria, could be joined by the Russian or Chinese governments in fighting a US invasion of Syria. The United States, for its part, would count on the support of the NATO countries including Turkey, as well as the Persian Gulf states such as Saudi Arabia and Qatar, which have armed and financed the US-backed Syrian opposition.

The bellicose rhetoric of the US and Turkish government thus threatens to touch off a military conflagration of dimensions that have not been seen since World War II.

Washington is making a confrontation all the more likely by economically strangling Iran with devastating sanctions, imposed primarily by the US and the European powers. The value of the Iranian rial dropped 40 percent against the dollar last week, while the price of basic goods has risen 80 percent over the past year. The brunt of Iran’s economic near collapse has been borne by the working masses. (See also: US wages economic war on Iran)

Washington is looking to deepen the economic damage in Iran by cutting out Iran’s remaining customers. Currently India makes dollar payments on oil from Iran through Halkbank in Turkey, but a proposal for new US sanctions could end that, under conditions where India purchases only 45 percent of its Iranian oil imports in its own currency, the rupee. Indian oil imports would therefore depend on a waiver of sanctions against Iran granted by the US, but which currently only lasts 180 days.

The EU is also considering banning the import of natural gas from Iran.

The potential for a conflict between Israel and Iran was highlighted recently when Israel shot down a small unarmed drone over the Negev desert yesterday. The drone crossed the Gaza strip and flew into southern Israel, apparently after having arrived from over the Mediterranean Sea. It was shot down several dozen miles from Israel’s Dimona nuclear reactor, the suspected source of Israel’s nuclear arsenal.

The Israeli government did not officially comment on who it thought was responsible for the drone flight. However, it flew fighter jets into Lebanese airspace after downing the drone, which suggests it was acting on reports in the Israeli press that the drone could have been launched by the Lebanese Hezbollah organization, an Iranian ally. Already during Israel’s 2006 invasion of Lebanon, Hezbollah launched an explosives-laden drone into Israeli airspace.

In September Hezbollah leader Hassan Nasrallah said his party could bomb the Dimona reactor.

Iran unveiled its first armed drones in 2010 and has since continued to develop that technology. It has reportedly also benefitted from reverse-engineering US drones that it captured when they overflew Iranian air space.

Earlier this month Iran announced the launch of a new drone with a range of 2,000 kilometers, armed with missiles. US reports allege that Iranian drones have practiced bombing runs that could be used against Dimona or Haifa.