Turkish president Tayyip Erdogan arrived in Tehran on Friday for a meeting with his Iranian and Russian counterparts to discuss Syria, the Tasnim news agency reported.

Russia and Iran have given military aid to Syrian President Bashar al-Assad in the country's seven-year-old conflict while Turkey has backed rebel forces.

The leaders are scheduled to discuss the looming military assault on Idlib in northwestern Syria, the country's last big rebel enclave.