Central Damascus 'hit by bomb explosion' Syrian state TV footage appeared to show the chaos following the explosion At least 13 people have been killed and many more injured by a powerful explosion in Syria's capital, Damascus, state media and activists say. A bomb is believed to have been detonated in a square in the central district of Marjeh. Civilians and security personnel are among the dead. Sporadic gunfire was heard in the area after the blast. On Monday, Prime Minister Wael al-Halqi survived a car bomb attack, which had targeted his convoy in the capital. The latest attack took place near a hotel, shopping centre and interior ministry building in Marjeh, a busy commercial district, the BBC's Jim Muir in Beirut reports. It is not yet clear what the target of the attack was or who was behind it, our correspondent says. However, it highlights that people in the centre of the city are no longer safe, he says. Widespread damage State television showed footage of wounded people being carried away amid widespread damage. The area was shrouded in dense smoke. Several vehicles could be seen burning and many buildings had shattered windows. The Syrian Observatory for Human Rights (SOHR) said the cause of the blast was a car bomb. The UK-based activist group monitors human rights violations on both sides of the conflict via a network of contacts across Syria. It estimates that March was the bloodiest month yet, with more than 6,000 people killed - a third of them civilians. Government forces and rebels have been fighting in and around Damascus for months, but neither have gained the upper hand. Monday's blast targeting the prime minister was the latest bombing inside government-controlled areas of the capital. The car bomb exploded as his convoy passed through the Mezzeh neighbourhood, reportedly killing a a number of people, including Mr Halqi's bodyguard. So far no group has said they carried out the latest bombings. But they do not appear to carry the hallmarks of attacks linked to the Free Syrian Army or the jihadist al-Nusra Front, one of the most prominent rebel groups, our correspondent says. Some opposition members accuse President Bashar al-Assad's government of planting the bombs in order to portray its struggle as one against terrorism, he adds. The UN says more than 70,000 people have been killed since the uprising against Mr Assad erupted in March 2011.