Syrian fighter jets fired at least two rockets at the Palestinian Yarmouk camp in Damascus.
It is the first time the camp has been targeted in such a way since the revolt against President Bashar al-Assad erupted last year, activists in the capital said.
They said 25 people were killed when at least one rocket hit a mosque in the camp sheltering refugees who fled the violence in nearby suburbs of Damascus.
Yarmouk, in southern Damascus, is part of an arc sweeping from the east to southwest of the Syrian capital where President Assad's forces have been trying for several weeks to push back rebels from the gates of his power base.
Neither side able to win - Syria's vice president
Syrian Vice President Farouq al-Sharaa has told a Lebanese newspaper that neither the forces of President Bashar al-Assad nor opposition fighters were able to win the war in Syria.
Mr Sharaa said the situation in the country was heading from bad to worse and that a "historic settlement", involving the formation of a national unity government "with broad powers", was needed to end the conflict, according to comments carried by al-Akhbar newspaper.
Mr Assad has ultimate power in Syria while Mr Sharaa, a Sunni Muslim, has a ceremonial role in a power structure dominated by Mr Assad's Alawite minority.
He has rarely appeared in public since the revolt against Mr Assad erupted 21 months ago.
The comments, excerpts from a longer interview due to appear in al-Akhbar's Monday edition, were Mr Sharaa's first public remarks since July last year.
Sources close to the Syrian government say he was among a group of politicians who had pushed for dialogue with the opposition and objected to the military crackdown against an uprising that began peacefully.
Mr Assad's government says it is fighting Islamist extremists backed by the Sunni rulers of Arab Gulf states and Turkey.
Several opposition sources say Mr Sharaa is believed to be under house arrest, and opposition activists have announced his defection several times this year.
"With every passing day the political and military solutions are becoming more distant. We should be in a position defending the existence of Syria. We are not in a battle for an individual or a regime," Mr Sharaa was quoted as saying.
"All the opposition cannot decisively settle the battle and what the security forces and army units are doing will not achieve a decisive settlement," he told the paper.