Violence has broken out in and around a rebel-held town near the Syrian capital Damascus, killing at least two people after nearly two weeks of calm.
The new conflict signalled an apparent collapse of a truce and an evacuation deal for opposition fighters to leave the area, state media and opposition activists said.
Syrian state TV said several air strikes hit Douma after members of the Army of Islam rebel group shelled government-held areas nearby, inflicting casualties.
The violence came after almost two weeks of relative peace in the last rebel-held town in the area known as eastern Ghouta, after the Russians agreed with the Army of Islam to evacuate the area towards rebel-held regions in the north of the country.
Earlier this week, hundreds of opposition fighters and their relatives left Douma towards northern areas controlled by Turkey-backed opposition fighters in the north.
The evacuations have been suspended since Thursday and state TV said Army of Islam members have refused to release scores of government supporters they have been holding for years.
There have been reports that the Army of Islam wants to negotiate a new deal, complaining of mistreatment by Turkish troops in northern Syria.
"There will be no further negotiations with terrorists over the evacuation deal. No one will be able to twist the army of the Syrian Arab Army," said a state TV reporter as sporadic explosions could be heard in the background.
"They will either release the detainees or the terrorists' hideouts and offices will be destroyed."
Army of Islam official Ammar al-Hassan said he had no information on whether the truce collapsed.
The Britain-based Syrian Observatory for Human Rights said two people were killed and 25 wounded in the air strikes that hit Douma on Friday afternoon, while Douma-based media activist Haitham Bakkar said at least four were killed and many others wounded.
Earlier on Friday, a bomb exploded near a mosque in Damascus, killing one person and wounding six others, according to state news agency Sana. It said the blast occurred in the north-eastern neighbourhood of Barzeh, close to the al-Khansaa mosque.
Such explosions have been rare in Damascus recently.
Barzeh is close to the eastern Damascus suburb of Harasta that opposition fighters evacuated last month following weeks of a crushing government offensive on eastern Ghouta.