BEIRUT (Reuters) - Tahrir al-Sham, an alliance of jihadist factions in Syria, on Saturday decried Turkey-backed Syrian rebel factions planning an operation in the northwestern Idlib province where it dominates, saying it would “not be a picnic” for them.

“The lions of jihad and martyrdom are waiting to pounce on them,” it added in a statement posted on a social media site.

Earlier on Saturday Turkish President Tayyip Erdogan said Syrian rebel fighters were preparing to launch “a serious operation” in Idlib backed by Turkish forces from inside Turkey’s borders.

The operation comes after an agreement last month between Turkey, Russia and Iran to set up a “de-escalation zone” in northwest Syria where Idlib is located to reduce warfare there.

Erdogan said Russia, which backs the Syrian government against rebel groups, would support the operation, but rebels taking part said Russia’s role was only in areas controlled by the Syrian government.

Tahrir al-Sham’s statement described the rebel groups involved as traitors, accusing them of working with Russia and the Syrian government, but without mentioning Turkey.