Syrian rebel forces have come under attack from Islamic State (IS) on the southern outskirts of Damascus.
Militants from the jihadist group are reportedly battling Jaysh al-Islam fighters in the Qadam district and those of Ajnad al-Sham in nearby Asali.
The fighting has brought IS closer than ever to the heart of the capital.
Correspondents say it is unclear whether the attacks will be limited to rebel-held areas or will later shift to the government-controlled city centre.
IS militants launched the assaults on Qadam and Asali over the weekend from Hajar al-Aswad, where they have been based since July 2014.
The pro-IS Amaq news agency reported that the jihadist group had captured half of Qadam and supporters posted photographs purportedly showing militants advancing through the district.
However, the Syrian Observatory for Human Rights (SOHR), a UK-based monitoring group, said they were only believed to control two streets.
There have so far been no reports of any clashes between IS and government forces in the area.
A Syrian military official told the AFP news agency that he was "very happy" about the jihadists' attacks on the rebels and that troops were "ready to react if they try to advance into government-held territory".
The Observatory said Qadam had been relatively quiet since a truce between rebel groups and government forces there a year ago.
In April, IS militants based in Hajar al-Aswad briefly took control of parts of the Yarmouk Palestinian refugee camp. That same month, they kidnapped two rebel fighters from Qadam and beheaded them.