At least 16 Syrian soldiers have been killed in a suicide bombing and fighting that followed in a Damascus suburb, activists say.
Earlier, the US urged the Syrian government to allow aid to reach starving civilians in Damascus.
Washington said the army|s months-long siege left many people in rebel-held areas in desperate need of food, water and medicine.
The blast triggered clashes at a checkpoint near the mainly-Christian area of Jaramana, the Syrian Observatory for Human Rights said.
State media blamed "terrorists" for the explosion but did not give details.
The UK-based Syrian Observatory for Human Rights, which relies on a network of activists inside Syria, said the suicide car bombing by the jihadist al-Nusra Front triggered heavy fighting at a key checkpoint between Jaramana and the rebel-held town of Mleha.
The report could not be confirmed.
Jaramana - a Christian and Druze area mostly loyal to President Bashar al-Assad, has previously been targeted by rebel groups.
In August a car bomb in the suburb killed 18 people.
Syria|s embattled President Assad has drawn support from Syria|s ethnic and religious minorities, including Christians and members of his Alawite sect, an offshoot of Shia Islam.
The rebel movement is dominated by Sunni Muslims, who are a majority in Syria.
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