Some 100,000 Syrian civilians have been displaced by a regime’s offensive on the country’s largest remaining rebel stronghold, the United Nations says. Since the start of November, fighting and air strikes have intensified in the north-western province of Idlib and neighboring parts of Hama and Aleppo. The UN says the situation for those forced from their homes is "dire". Some 2.65 million people are living in north-western Syria, including 1.16 million internally displaced people (IDPs), according to the UN. In the past year, more than 500,000 people have arrived in rebel-held areas from other parts of the country, leaving already-stretched humanitarian organizations struggling to help those in need. The escalation in fighting between pro-regime forces and rebels has caused civilian casualties, damaged infrastructure and led to mass displacement. The UN said last week that 60,000 people had fled their homes since 1 November. On Wednesday, an official told the BBC the figure had climbed to 100,000. The UN High Commissioner for Human Rights, Zeid Raad Al Hussein condemned the upsurge in civilian casualties in Idlib. Earlier, Turkey’s foreign minister told Anadolu news agency that the advances by Syrian regime could not have taken place without Russian and Iranian support, and demanded they "fulfil their responsibilities". Mevlut Cavusoglu warned that the Idlib offensive was endangering efforts to broker a political solution to the conflict, including a planned "national dialogue" congress in the Russian resort city of Sochi later this month. "It’s not just a simple air strike. The regime is moving in Idlib, the intent here is different," he said. "If the aim here is to make some unwilling opposition groups go to Sochi, it will backfire."