Earlier reports on Friday indicated that Alloush along with seven other terrorist field commanders and 10 militants had been killed.
"The Syrian air force has carried out airstrikes, following intelligence reports and assistance by respected citizens, targeting terrorist groups in the eastern suburb of Damascus. As a result, terrorist Zahran Alloush was killed," the army said in a statement reported by Sputnik News.
Jaysh al-Islam named Issam al-Buwaydani (also known as Abu Humam) from the city of Douma northeast of Damascus as its new leader.
Jaysh al-Islam, a terrorist group formed by a merger of several Syrian opposition groups in 2013, is notorious for its atrocities, including the public executions of prisoners, drawing comparisons with the Daesh militant group, which is outlawed in many countries.
Jaysh al-Islam has repeatedly shelled Damascus and its suburbs with mortar rounds and rockets, killing hundreds of civilians.