Hezbollah must provide answers over the killing of political commentator and publisher Lokman Slim, Lebanese politicians said on Thursday as the president demanded an investigation. Slim, 59, was found shot dead in his rental car in south Lebanon on Thursday, a day after his family said he went missing The Kataeb party, a leading member of the opposition, said Slim’s killing was an attempt to silence critical figures and to block the rise of a sovereign, free and independent state. The party’s leader and former MP Sami Gemayel told The National that Mr Slim "paid the price on behalf" of opposition activists and groups demanding a strong independent Lebanon. Mr Gemayel, however, stopped short of directly accusing the Iran-backed party of involvement in the murder but added that ”pointing fingers at Hezbollah is understandable and normal given the circumstances.” Former MP Fares Souaid, a prominent member of the alliance that led the campaign demanding an end to Syria's decades-long occupation of Lebanon after the assassination of Rafik Hariri in 2005, said Hezbollah was the primary suspect behind Slim's killing. “The assassination took place in an area dominated by Hezbollah, so either Hezbollah tells us how the murder happened or let them bear direct responsibility,” Mr Souaid said just hours after news of the killing broke. He told <em>The National</em> that Slim's killing appeared primarily aimed at intimidating opposition forces in the Shiite community. His killing should be a wake-up call for opposition groups to unite, Mr Souaid said. For its part, Hezbollah condemned the murder in a statement released on Thursday evening, and called on judicial and security agencies to "work quickly to detect and punish the perpetrators". President Michel Aoun ordered the state prosecutor to investigate the case while caretaker prime minister Hassan Diab said those responsible should be held accountable. Slim was a vocal critic of Hezbollah and the target of several campaigns by the group’s supporters who have long accused him of serving a foreign agenda, a reference to the US, which classifies the Shiite party as a terrorist organisation. His killing sparked fears of a renewed wave of assassinations of anti-Hezbollah activists and politicians, similar to the series of murders that followed the assassination of Hariri in 2005. Fifteen years later, an international tribunal convicted a Hezbollah member of taking part in the murder. Hezbollah, which denies any role in the assassination, refuses to hand over the convicted member. Former prime minister Fouad Siniora, a member of prime minister-designate Saad Hariri’s Future Movement, said the murder evoked memories of past events and also said it was aimed at intimidating opposition figures. Mr Siniora urged a quick and transparent investigation into Slim’s murder. The failure to conduct such an inquiry, he said, will give credibility to accusations directed at those “who control the south and its villages with weapons”. Former MP Paula Yacoubian, however, said she fears the investigation into Slim’s killing would face a similar fate as that into the Beirut port blast. “Killing is their habit. Unfortunately, there is no hope in the investigation, which will follow [a similar path] to the port probe …” Ms Yaacoubian wrote on Twitter. Slim's murder prompted concerns among diplomats. “Huge sadness and concern over the news of the murder of Lokman Slim. My condolences and thoughts go out to his wife, family and loved ones,” wrote Anne Grillo, France’s ambassador to Lebanon. US ambassador Dorothy Shea said threats and intimidation of the kind Slim endured before his death was "unacceptable". "This assassination was not just a brutal assault on an individual, but a cowardly attack on the principles of democracy, freedom of expression, and civic participation," she said in a statement from the US Embassy in Beirut. "It is also an attack on Lebanon itself." She called for an "expeditious" investigation into Slim and others' killings. UN spokesman Stephane Dujarric on Thursday also condemned the murder and urged Lebanese authorities to carry out a "thorough, transparent investigation" leading to an "efficient judicial process".