group vowed to intensify its fight against the US-led coalition and Kurds in
eastern Syria, in a video posted Sunday on its Telegram channel.
"The fire of the battle between us and them has been reignited and will intensify," the jihadist group said, addressing what it called "soldiers of Islam" and residents of the caliphate.
ISIS took swathes of oil-rich land in Iraq and Syria in a lightning 2014 offensive.
The jihadists lost the last shred of their self-declared "caliphate" in late March, when Syria's Kurds took the village of Baghhouz in Deir Ezzor province with support from coalition air strikes.
But ISIS retains sleeper cells and has orchestrated a series of car bomb and arson attacks in eastern and northeastern Syria since its territorial defeat.
In Sunday's video – the second since the fall of Baghouz – ISIS accused coalition countries of having entrapped its local adversaries, including the Kurds.
"They have been thrown into the flames of a fierce war that will leave them without tail or head," ISIS warned.
The video includes decapitations and the shooting to death at close range of people presented as kidnapped Kurdish fighters.
ISIS released a video in late April – shortly after claiming deadly attacks in Sri Lanka – in which leader Abu Bakr al-Baghdadi purportedly appeared, pledging vengeance and a "long battle" ahead.
A US Defense Department report said this month that ISIS was "resurging" in Syria, while it had "solidified its insurgent capabilities in Iraq".