A car bombing near Syria's ruling party headquarters in Damascus has killed 53 people, according to state media, while mortar rounds exploded near the army's central command in the city.
It was the third straight day of attacks on the centre of the capital, among the deepest and fiercest on the heart of President Bashar Assad's seat of power during the civil war.
The car bombing was the deadliest attack inside Damascus in nine months and within hours, two other bombings and a mortar attack on the military compound followed.
While no one group has claimed responsibility, the attacks suggest that rebel fighters who have got bogged down in their attempts to storm the capital are resorting to guerrilla tactics to loosen Mr Assad's grip on the capital.
In the southern town of Daraa, where Syria's uprising began nearly two years ago, British-based activists said 18 people were killed in an air strike including eight rebel fighters, three medics, one woman and one young girl.
The day's deadliest attack struck a main street on the edge of central Mazraa neighbourhood, near the headquarters of Mr Assad's Baath party and the Russian Embassy, as well as a mosque, a hospital and a school.
TV footage of the blast site showed firemen dousing a flaming car with hoses and lifeless and dismembered bodies blown into the grass of a nearby park. The state news service, SANA, published photos showing a large crater in the middle of the rubble-strewn street and charred cars holding blackened bodies.
Witnesses said a car exploded at a security checkpoint between the Russian Embassy and the central headquarters of Assad's ruling party. "It was huge. Everything in the shop turned upside down," one local resident said. He said three of his employees were injured by flying glass that killed a young girl who was walking by when the blast hit.
Ambulances rushed to the scene of the blast, which shattered windows and sent up a huge cloud of smoke visible throughout much of the city, witnesses said. State TV called it a "terrorist" attack by a suicide bomber. It said at least 53 people were killed and more than 200 wounded. The Britain-based activist group the Syrian Observatory for Human Rights said at least 42 people were killed, most of them civilians. Some members of the Syrian security forces were also killed, it said.
The bombing appeared to be the second most deadly in the Syrian capital since the uprising against Mr Assad began 23 months ago. Fifty-five people were killed in the first, a double suicide bombing outside an intelligence building in May, 2012.