The blast in Douma came nearly two hours after Russia's deputy foreign minister called on the United States and Europe to take "serious" steps to combat terrorism during a visit to Damascus, warning that several Middle Eastern countries are threatened.
"Russia will not stand idle toward attempts by terrorist groups to spread terrorism in regional states," Sergei Ryabkov told reporters, apparently referring to the rapid advance of the extremist Islamic State of Iraq and the Levant across eastern Syria and northern Iraq.
Both Russia and Assad's government have portrayed the civil war in Syria as a struggle against foreign-backed "terrorists," the word Damascus applies to all rebels fighting to end the Assad family's four-decade reign.
The market blast in Damascus killed at least two people and wounded others who were rushed to nearby makeshift hospitals, according to the Britain-based Syrian Observatory for Human Rights and amateur videos released by activists in the area.
The Observatory said the explosion caused extensive damage. The Observatory and an activist in the nearby suburb of Saqba who goes by the name of Abu Yazan said the Islamic State is believed to be behind the blast, because of a rivalry with other rebel groups in the area.