ISIS on Thursday denied being behind a suicide blast that hit the governing council of insurgent-held Idlib in northwest Syria on Tuesday, its Amaq news service said.
The explosion, which targeted the "Salvation Government" building of the Hayat Tahrir al-Sham militia in Idlib this Tuesday was not connected to fighters of the ISIS," Amaq said, citing a security source.
ISS rarely denies carrying out attacks.
Idlib and adjacent areas in northwest Syria are the last stronghold of rebels who rose up against President Bashar al-Assad in 2011. Tahrir al-Sham this month seized control of most of Idlib after fighting with Turkish-backed insurgents.
No other group has claimed responsibility for Tuesday's blast. There have been frequent bombings and shootings targeting officials in rebel groups in Idlib over the past year.
The Salvation Government runs the areas held by Tahrir al-Sham, a jihadist alliance that includes the former Syrian al Qaeda affiliate, the Nusra Front.
A war monitor, the Syrian Observatory for Human Rights, said on Tuesday the blast had killed one person and injured three others, and that ISIS was suspected.
ISIS has lost almost all its territory in Syria, but still claims responsibility for a string of bombings targeting U.S.-backed, Kurdish-led militia in northeast Syria.