The 27 December assassination in central Beirut of Mohamad Chatah, a senior adviser to Lebanon’s Sunni-led Future Movement leader Saad Hariri, has revived fears of a resumption of the targeted killings of leaders associated with the opposition March 14 camp. Meanwhile, Lebanon is gearing up for the start of the Special Tribunal on Lebanon (STL) to investigate the killing of the former prime minister, Rafik Hariri.

Chatah was a former finance minister under March 14 prime minister Fouad Siniora, and considered a voice for moderation in the increasingly sectarian-charged Lebanese political scene. A perceptive and articulate observer of the region’s politics, regularly briefing journalists (including MEED), Chatah had previously worked for the Washington-headquartered IMF and lectured in economics at the University of Texas. His death robs Lebanese politics of a robust intellectual who had earned widespread international respect.

Even critics of the Sunni-Christian March 14 alliance acknowledge that Chatah was an unlikely candidate for assassination. “He was a technocrat and never uttered a single sectarian word, unlike some other Future MPs,” says Amal Saad-Ghorayeb, a Beirut-based political analyst sympathetic to the Hezbollah-backed March 8 bloc. She argues that the murder is part of a wider campaign to destabilise Lebanon and provoke sectarian animosity.

The Beirut rumour mill has been in overdrive since the bombing, with suggestions that Siniora himself – another prominent Sunni moderate – was the intended victim.

Either way, the damage wrought to Lebanon’s body politic is substantial. The assassins have struck a crushing blow at the mainstream political faction allied to Saudi Arabia and the West at a particularly critical time in Lebanon’s history, with the STL preparing to commence its proceedings on 16 January.

Critics of Hezbollah and its Syrian backers believe the killing of a mainstream moderate figure was intentional. “We are seeing the targeting of Sunni moderates as a policy,” says Albert Kostanian, a member of the politburo of the Kataeb Party, a Christian faction that forms part of the March 14 movement. “It’s important for the Syrian regime and the constellation of groups that follow it to show that Sunnis cannot be moderate.”

The regime of Syria’s President Bashar al-Assad fostering Jihadist extremism in the country – such as its releasing prisoners associated with the more militant Syrian rebel factions to foment dissent in opposition ranks – is viewed as part of the same strategy.

Another possible objective in the Chatah’s slaying was to further destabilise the Lebanese state and its increasingly fragile institutions. Critics accuse Syria’s ally, Hezbollah, of doing everything in its power to prevent the formation of a cabinet of technocrats, and wanting the perpetuation of the current caretaker government (dominated by March 8 politicians).

The timing of the assassination, on the very day the Finance Ministry announced the transfer of the Euros 29m that constitutes its share of the funding for the STL, may be significant. With five Hezbollah members accused of involvement in Hariri’s killing, opposition figures suspect the attack was also intended as a message to the tribunal. “They are showing that everyone is vulnerable and the tribunal will not protect anyone,” says Kostanian.

The concern is that it is unlikely to be the last such attack. Chatah was the 11th senior Lebanese individual associated with the March 14 movement to be killed since 2005. However, Chatah’s killing was the first since Brigadier General Wissam al-Hasan, chief of the Intelligence Bureau of the Internal Security Forces, was assassinated in East Beirut back in October 2012.

One problem is that Lebanese security forces are not in full control of the Syrian border and are unable to guarantee the security of leading critics of the Al-Assad regime.

The only significant breakthrough against the assassins came in August 2012. Michel Samaha, a former government minister associated with the March 8 block, was arrested on accusations of transporting explosives from Syria to Lebanon in an attempt to assassinate Lebanese political and religious leaders. His trial has yet to get under way, however.

For many Lebanese, the best hope of quelling rising tensions is for the tentative rapprochement between the US and Iran to gain traction, which might provide the space for Tehran to rein in its Lebanese and Syrian proxies.

That seems a long way off. More worryingly is that the 27 December car bomb, in a prominent downtown location, indicates the capital itself is no longer regarded as off limits to terrorist attacks. This point has been reinforced by the deadly bomb blast that targeted Iran’s Beirut embassy in November.

The prospect of intensifying Sunni-Shia tit-for-tat killings being played out on the streets of Beirut is a dismal prospect for Lebanon, where the economy is suffering badly from the worsening security situation.

The squeezing out of moderate voices such as Chatah can only make things worse. As the Lebanese political commentator Michael Young tweeted in the immediate aftermath of Chatah’s death: “Target the moderate Muslims, such as Mohaad Chatah, and don’t be surprised when the only ones left are the radical jihadists.”