Syrian rebels and jihadists from the Islamic State have agreed a non-aggression pact for the first time in a suburb of the capital Damascus, a monitoring group said on Friday.
The Syrian Observatory for Human Rights said the ceasefire deal was agreed between IS and moderate and Islamist rebels in Hajar al-Aswad, south of the capital.
Under the deal, "the two parties will respect a truce until a final solution is found and they promise not to attack each other because they consider the principal enemy to be the Nussayri regime."
Nussayri is a pejorative term for the Alawite sect, an offshoot of Shiite Islam to which President Bashar al-Assad belongs.
Syria's armed opposition initially welcomed jihadists including Islamic State members in their fight against Assad.
But the group's harsh interpretation of Islam and quest for domination of captured territory sparked a backlash against it that began in January.
A coalition of rebel groups pushed IS out of much of northern Syria, but it has recaptured much of that territory in recent months and has a strong presence in Hajar al-Aswad.
More than 180,000 people have been killed in Syria since the beginning of the uprising against Assad that began in March 2011.