In an earlier tweet he had written: "Arafat, then Assad then Nasrallah. If Lebanon is not saved from its current path, history will tell how the third blow led to its downfall. According to reports he was killed as he headed to Saad Hariri's mansion to attend a meeting of the pro-Western March 14 coalition. The coalition was quick to imply Hizbollah's involvement in the killing. Damascus, and Hizbollah in turn, denied the accusations, calling the act a "heinous crime." Caretaker Prime Minister Najib Mikati said: "We condemn the assassination of former minister Mohamad Chatah and condemn acts of violence and murder, but [hope] they don't lead to more war and devastation damaging our homeland." Four members of Hizbollah, which is close to the Syrian government of President Assad, have been accused of carrying out the murder. It was not immediately clear yesterday why Mr Chatah was targeted, but some analysts suggested it could be tit-for-tat revenge for the assassination of a Hizbollah commander last month. The blast, which at 9.40 in the morning, went off just hundreds of yards from the parliament building but was heard across the city. A large mushroom cloud could be seen from miles away after one of the most powerful explosions to hit the capital in recent years. Cars were still on fire and bodies in the street of the upscale Downtown area when reporters arrived on the scene. At least 70 people were injured, according to estimates. The security situation in Lebanon, which had recovered after the civil war and again after the killing of Rafiq Hariri, has fast deteriorated in the last three years. As clashes in neighbouring Syria turned to civil war, Lebanon took sides, with Sunni politicians and groups, including supporters of Mr Hariri, sending arms to the rebels and Hizbollah sending men to fight alongside troops loyal to Assad. There have also been previous car bombings - most notably, a double suicide attack last month on the embassy of Iran, another supporter of Assad, claimed by an al-Qaeda-affiliated Sunni militant group. The loss of Mr Chatah will be a serious blow to the Future Movement. William Hague, Foreign Secretary, described the explosion as "sad news." "My thoughts and sympathy with the people of Lebanon and the families of all those killed," he said.