Syrian state television says a car bomb has exploded in central Damascus.
Reports say at least 15 people were killed and more than 50 others wounded.
State television showed wrecked cars in flames and said the explosion occurred on April 8 near a school in Sabaa Bahrat, considered the capital's main business district.
The Syrian central bank and Finance Ministry are also in the area.
A correspondent with the AFP news agency reports the blast caused extensive damage and was followed by intense gunfire.
Witnesses reported large plumes of smoke were rising from the area.
Syrian rebels, who have been fighting for nearly two years to oust President Bashar al-Assad, have pushed into areas surrounding the heart of the capital and launched mortar and car-bomb attacks.
Meanwhile, UN Secretary-General Ban Ki-moon says he is ready to send inspectors on 24 hours' notice to examine claims about chemical weapons being used in Syria.
Speaking in The Hague on April 8, he said a team of inspectors is standing by in Cyprus and that "all we are waiting for is the go-ahead of the Syrian government to determine if any chemical weapons have been deployed."
He said that for now, deployment still must await "technical and legal" negotiations with Damascus about the terms of such a mission.
Ban spoke at the headquarters of the Organization for the Prohibition of Chemical Weapons in the Dutch capital.
Both the Syrian government and rebels have accused each other of using chemical weapons, but no claims have yet been independently investigated or verified.
Based on reporting by Reuters, AP, AFP, and dpa