BEIRUT A bomb killed 13 people in central Damascus on Tuesday, state television said, a day after Prime Minister Wael al-Halki survived an attack on his convoy in the Syrian capital.
State-run Suriya television said 70 people were wounded, several critically.
The British-based Syrian Observatory reported nine dead civilians and three security personnel but said the toll was likely to rise.
Pro-government Al-Ikhbariya television showed firefighters running through thick smoke after the blast in Marjeh Square. Two bodies could be seen on the ground.
The target of the attack was not immediately clear. Footage showed the former Interior Ministry building near the site of the blast on one of the capital's main roads.
Interior Minister Mohammed al-Shaar said the bombing was a "bankrupt response" to recent gains by the Syrian army against rebels in the areas surrounding the city centre.
Shaar, who was wounded by a car bomb blast in December, said the United States, the West and Israel were directing the group that carried out the bombing.
Monday's attack on the prime minister's convoy killed six people in what has become a common tactic by rebels.
A resident of Damascus, who lives one mile (1.6 km) from the blast site, said the explosion shook the doors of her house.
"It must be huge for me to hear it like that. Casualties must be horrific because it is a super busy square at this time of day," she said over Skype.
Rebels have increased their attacks on Damascus, which include mortar fire from the contested suburbs, in a civil war that has cost more than 70,000 lives according to U.N. estimates. A bomb in July killed four of President Bashar al-Assad's aides, including his brother-in-law Assef Shawkat and the defence minister.