Russian jets bombed villages and towns near the northwestern Syrian city of Idlib on Sunday, killing at least nine civilians and wounding dozens in a major flare-up of violence in the country’s last opposition stronghold, witnesses and rescuers said.

War planes flying at high altitude, which tracking centres said were Russian Sukhoi jets, dropped bombs on a vegetable market in Jisr al-Shughour while it was crowded with shoppers ahead of the Muslim Eid feast, leaving at least nine dead and 30 injured, the Western-backed White Helmets emergency response group said.

Witnesses and rescuers said jets also hit villages in the mountainous Jabal al Zawya region and the western outskirts of Idlib city, which fall within a buffer zone carved out by Russia and Turkey that ended major fighting nearly five years ago.

No immediate comment was available from Russia or its allies in the Syrian army, whose artillery pounded rebel areas in the countryside west of Aleppo.

During past outbreaks of fighting, Damascus and Russia have said they only target insurgent groups and deny indiscriminate attacks on civilians.

More than 4 million people live in the densely populated opposition-held northwest along the Turkish border. Most were driven there by successive Russian-led campaigns that regained territory seized by rebels.

Damascus has in recent rounds of Russian-brokered talks with Ankara demanded that Turkey withdraw a formidable military presence in the last foothold of the Syrian rebellion.