Syria prepared on Saturday to bury 26 people killed in a Damascus suicide bombing as the authorities vowed an "iron fist" in response to the "terrorist" attack, the second such incident in two weeks.
The opposition pointed the finger at the regime itself, as it did after similar attacks on December 23, in which 44 people died.
The bomber blew himself up near a school in in the historic Midan quarter, Interior Minister Lieutenant General Mohammad al-Shaar was quoted as saying.
Sixty-three people were also wounded, the government said.
Another 17 civilians were shot dead on Friday in the daily unrest, activists said.
The interior ministry branded the bombing "a new terrorist escalation" and said more than 10 kilos (22 pounds) of explosives were used.
"We will strike with an iron fist all those who undermine the security of the nation," a ministry statement said.
Opposition factions blamed President Bashar al-Assad's government for the bombing and called on Arab and Western forces to end the bloodshed.
"We hold the regime, its agents and its gangs, fully responsible for this crime," said the Muslim Brotherhood, which had also accused the government of orchestrating twin suicide attacks in Damascus on December 23.
The umbrella Syrian National Council, which includes the Brotherhood, said Friday's bombing "clearly bears the regime's fingerprints."
The United States condemned the attack, again calling for Assad to step down, while UN chief Ban Ki-moon said "all violence is unacceptable and must stop immediately."
Assad ally Iran condemned the "terrorist attack."
Foreign ministry spokesman Ramin Mehmanparast said: "Without doubt, the unity and vigilance of the Syrian government and people are disappointing the enemies of Syria who think only of internal war, breaking up the country and making it submit to the demands of the axis of America and Zionism."
Damascus blamed Al-Qaeda for December's twin bombings, while the opposition accused the government.
Friday saw a similar exchange of accusations.
The ruling Baath party called the attack "a terrorist act that is a part of the plot hatched against Syria," state media reported.
The plot "coincides with the statements made by opposition groups and by French and American officials," it said.
The Muslim Brotherhood called for an international probe, claiming the attack benefited the regime.
The SNC said the UN Security Council had to take up the matter of the bloodshed, which the world body estimated in December had killed more than 5,000 people since pro-democracy protests erupted in March.
It said "a joint effort between the Arab League and the United Nations Security Council represents a first step toward the urgent and necessary measures to assure the protection of civilians, and to ensure that the regime does not commit additional bombings and killings."
Activists have called for an Arab League observer mission to admit its failure to stem nearly 10 months of bloodshed and hand over to the United Nations.
UN leader Ban reaffirmed an offer to train the Arab League observers.
The Arab mission has been in Syria since December 26 trying to assess whether the government is complying with a peace deal aimed at ending its deadly crackdown.
But there has been no let-up in the violence and new criticism of the observers.
The Arab League is to meet in Cairo on Sunday to discuss the mission.
Qatari Prime Minister Sheikh Hamad bin Jassem al-Thani, who heads an Arab League task force on Syria, has acknowledged "mistakes" in the monitoring mission.