Yesterday's air strikes were carried out in Douma, a satellite suburb northeast of the capital that has been under siege for more than a year.
"The toll from regime air raids on Douma has risen to 42 dead, including seven children and two women," said the Syrian Observatory for Human Rights, which yesterday had given a death toll of 17.
Among those killed were an unspecified number of rebels who have been fighting to oust the regime of President Bashar al-Assad for more than three years, said the Britain-based group.
People could be seen carrying the charred remains of victims amid scenes of panic as firefighters battled to put out blazes in several buildings.
The Observatory says more than 180,000 people have been killed in the Syrian conflict since it erupted in March 2011, while the United Nations puts the figure at 191,000.
Opponents of Assad took up arms in response to a bloody crackdown on peaceful pro-democracy protests inspired by the Arab Spring uprisings.