The assassination of the Lebanese intelligence chief, General Wissam al-Hassan, has stoked fears that the Syrian regime, with its back to the wall, is deliberately trying to "internationalise" the civil war as a means of ensuring its survival.

President Bashar al-Assad is effectively raising the price that hostile neighbouring countries and the major powers must pay for his overthrow, by actively fuelling the region-wide conflagration that UN envoy Lakhdar Brahimi says could be sparked by unchecked violence inside Syria.

The potential cost in Lebanon became clearer at the weekend after the Beirut assassination. Sunni Muslim and Christian groups opposed to Syria's Alawite regime and Lebanon's pro-Syrian government took to the streets. Hezbollah, the Iranian-backed Shia movement that is Lebanon's most powerful military force, is widely blamed for Hassan's death.

Saudi Arabia and western allies such as the US and France have invested much time and trouble trying to ensure politically fragile Lebanon does not return to sectarian warfare. The murder in 2005 of the country's prime minister, Rafik al-Hariri, also blamed on Assad, was a setback for Syrian influence there. But Hassan's killing is a reminder that Damascus still has the ability to fatally destabilise its one-time satrap.

"The murder of Hassan, a Sunni, who was killed by a car bomb on Friday, was yet another indication that the Syrian conflict is starting to spill into Lebanon," wrote Amos Harel and Avi Issacharoff in Haaretz. "Lebanese politicians and commentators … all agree on one thing: that Lebanon is being pulled into the Syrian turbulence, and that the chances of a civil war being reignited on Lebanese soil is greater now than at any time since Hariri was murdered."

The Syrian regime has already impressed on Turkey how big a price Ankara may have to pay for its departure, which Turkish leaders have been demanding with ever greater vehemence since bilateral relations imploded last year.

A series of incidents along the two countries' shared 900km border culminated this month in days of artillery exchanges after Syrian army units shelled a town inside Turkey, killing five civilians. Damascus claimed the initial shelling was an accident. In an interview with the Guardian last week, Ahmet Davutoglu, Turkey's foreign minister, asked why, if that was the case, the Syrian units kept on firing?

Turkish officials also suspect Assad is using the ever-increasing flow of refugees into Turkey, Lebanon and Jordan as an indirect way of applying pressure on his enemies. Davutoglu fears a humanitarian catastrophe this winter if nothing changes – and wants an international response. There are already 150,000 displaced Syrians on Turkish soil.

"We hope the US and other countries will have a firmer position regarding the humanitarian disaster that is threatening regional stability … I agree with Brahimi, we have a great concern this could set the region ablaze. All the neighbouring countries will be affected," Davutoglu said.

Turkey furnishes another example of how Assad is deliberately internationalising the conflict. Officials say Syria is aiding and abetting Iraq-based Kurdistan Workers' party (PKK) separatist fighters, whose campaign of violence inside Turkey has reached a 10-year high this year, in retaliation for Turkish support for the Syrian opposition. Assad's crude message to Ankara: back off, or face escalating strife at home.

Similar calculations may lay behind the reportedly reduced enthusiasm in Saudi Arabia and other Gulf states for arming Syria's rebels. Damascus's claim that the arms are going to hardline Salafist groups linked to al-Qaida, as happened when the west armed Afghanistan's mujahideen in the 1980s, have rung alarm bells in Washington.

If there is one thing the US hates more than a bloodthirsty dictator, it is the thought he might be replaced by crazed jihadis pledged to wage war on the west. Seen this way, Assad's survival might be judged the lesser of two evils.

In many respects, the Syrian war is already "internationalised". The US and its European and Gulf allies have lined up behind the Syrian opposition, and are helping it to varying degrees.

Russia and its old-new Middle East ally, post-occupation Iraq led by Shia prime minister, Nouri al-Maliki, are firmly in Assad's camp, for a variety of geostrategic (read anti-American) reasons.

And behind Assad stands Iran, determined to sustain its principal Arab ally, eager (as ever) to thwart the Sunni monarchies of the Gulf and their American friends, and fearful that an Arab spring success in Syria would leave the authoritarian Tehran regime in the cross-hairs.

If Assad falls, Ayatollah Ali Khamenei and the mullahs would be next. True or not, that is what Iran's clerical leadership believes. Given the ever-present possibility of an Israeli or American military strike, a region-wide war holds no terrors for them.

By constantly raising the stakes for all concerned, Assad hopes he can somehow cling to power – or take everyone down with him.