BEIRUT - Syrian opposition activists say the Islamic State group has regained control of the ancient town of Palmyra nine months after it was driven out by Russian-backed Syrian government forces.

The Britain-based Syrian Observatory for Human Rights and the Palmyra Coordination group say IS militants fought their way into the town on Sunday, forcing government forces to retreat to the south.

Russia had earlier said that it helped Syrian troops repel an attack on the town by launching more than 60 airstrikes. IS has been advancing on the town in recent days, capturing areas on its outskirts at a time when Syrian forces are focused on driving rebels out of the northern city of Aleppo.