In northwestern Syria, 68-year-old Abu Khaled was among dozens to have set up camp in a field, hoping that Turkish soldiers nearby would shield him from bombardment by Bashar al-Assads regime. In the countrys last major opposition bastion of Idlib province on Turkeys border, civilians are scrambling to protect themselves from a possible Russian-backed regime offensive, reported Agence France Presse. Fears have mounted that any attack on the region of nearly three million people could spark one of the worst humanitarian disasters of Syrias seven-year civil war. Dressed in a long white robe and a chequered red-and-white headscarf, Abu Khaled sat by his tent pitched in a field in the southeast of Idlib. Around him, children played between poles covered in flowery bedsheets and pitched for shelter in the red earth. One dangled back and forth on an improvised swing, while a woman prepared food in a large saucepan on an open fire. "There was bombardment of our villages so we came here, near the Turkish outpost," Abu Khaled said. "Its to protect us," he said, referring to the monitors deployed by rebel backer Turkey just hundreds of meters (yards) away. Last year, Ankara and regime allies Moscow and Tehran made Idlib a "de-escalation zone" under a deal that saw Turkish monitoring posts set up in the province. The United Nations has warned that any regime attack on Idlib could displace up to 800,000 people, and urged key players to intervene to avoid a "bloodbath". Aid agencies urged world powers to avoid "the greatest humanitarian catastrophe in Syrias seven-year war". Humanitarian workers "are already overwhelmed trying to provide shelter, food, water, schooling and healthcare," eight agencies said in a joint statement. Around half of the residents of Idlib and adjacent areas have already lost their homes in the conflict, the UN says. Russian-backed regime troops have massed around the province in recent weeks, after ousting opposition factions from other parts of the country. The timing and scope of any attack remain unclear, but healthcare and aid workers are preparing for the worst, said AFP. At a hospital in the provincial capital of Idlib this week, staff worked as usual. Two doctors wearing grey scrubs operated on a patient, while a staff member tested a girls eyesight in another room. But their hospital, like others in the province, is drawing up a contingency plan in case the surrounding area comes under attack. "Every hospital needs to have a special emergency plan," said Mustafa al-Eido, the deputy head of healthcare in Idlib province. With no means to defend the hospitals against regime or Russian air strikes, they would have to reduce staff or redeploy doctors and nurses to other locations. "You cant fortify against Russian military equipment," Eido said. In the first six months of this year, 38 attacks hit medical infrastructure in Idlib province, most blamed on the regime or Russia, the UN says. To better respond to air strikes, a joint operations committee has been set up to coordinate between the health services 50 ambulances and rescue organizations such as the White Helmets, Eido said. Hospitals are grappling with severe shortages of medicines and also trying to stock up on supplies to deal with any chemical attack, he said. Assads regime has been repeatedly accused of using chemical weapons during the conflict, including in an attack that killed more than 80 people in the Idlib province town of Khan Sheikhun last year. Since then, staff from 16 hospitals in Idlib and adjacent areas have trained with the World Health Organization in Turkey on how to treat victims of any toxic attack, Eido said. Aid workers are preparing to deal with any sudden exodus of civilians. Just outside Idlib province, at a camp for the displaced, its director Yussef Nur inspected reserve supplies of thin foam mattresses, woolen blankets and large outdoor plastic sheets. "Weve planned for any sudden displacement of people," he said. "We now have around 700 people at the camp" in Mizanaz in neighboring Aleppo province. But "we could take in 1,800 to 2,000 more".