Abu Jabber has a plan to escape the Syrian regime's advance: he has built a ladder from rusty metal for him and his 11 children to climb over the Turkish border wall. Six months ago, the family fled fighting in Idlib province in north-west Syria, seeking shelter near the border village of Kafr Lusin, where dozens of families live in an informal camp for the displaced. Newcomers live in tents while others, such as Abu Jabber, his children and his parents, have built makeshift homes at the foot of a cement wall that separates Turkey from Idlib province. Turkey, which already hosts the world's largest number of Syrian refugees with about 3.7 million people, has placed barbed wire and watchtowers along the wall to prevent any more crossings. Ankara fears an offensive launched in December by Russian-backed Syrian government forces against the last major rebel and extremist bastion in Syria could spark another influx of refugees. Damascus has this month escalated its offensive and seized dozens of villages and towns in Idlib and the neighbouring province of Aleppo. "When I saw that the situation was getting worse, I decided to build a ladder," said Abu Jabber, standing outside his new home among the olive groves of Kafr Lusin. "I did this in case the regime makes further advances." He said his family would climb the border wall "to protect our children", pointing to the ladder he made with bits of rusty metal. Abu Jabber said there was no other solution. "Either they [regime forces] kill us all or we enter Turkey," he said. He and his family have been displaced several times since Syria's war erupted almost nine years ago. Half of the three million people living in Idlib are displaced from other regions of Syria, having abandoned areas recaptured from rebels by government forces. Abu Jabber, whose home was originally in Hama province, said his son, 10, whose hand was amputated, lost an eye in regime bombardment. Trying to escape to Turkey also carries its risks. Turkish border guards have sporadically opened fired on Syrian civilians attempting to cross the border illegally. "Going to Turkey is not really a choice, but I need security. I want to be able to sleep, I need shelter, heating and food," Abu Jabber said. The regime offensive has displaced about 900,000 civilians since December and an estimated 170,000 of them are living out in the open, the UN said. The UN and aid groups have called for a ceasefire and the Norwegian Refugee Council warned the regime offensive could lead to a "bloodbath". "Our fear now is that a full-on offensive could lead to the worst catastrophe of Syria's brutal war, an out-and-out bloodbath for displaced civilians," NRC chief Jan Egeland said this month. UN High Commissioner for Refugees Filippo Grandi urged Syria's neighbours to take in more of the displaced. "I am appealing for neighbouring countries, including Turkey, to broaden admissions, so that those most in danger can reach safety, even knowing that capacities and public support are already strained," Mr Grandi said. In Kafr Lusin, tents made of plastic sheeting are home to families of 10 people or more. Abdel Razzak Sallat arrived at the informal camp two weeks ago from the town of Binnish, about 8 kilometres north-east of Idlib city, along with his eight children. They now share a tent with his sister-in-law's family. In all, 19 people are crammed together under the canopy. Their belongings, including flimsy mattresses and blankets, are piled up on one side, while another area has been turned into a makeshift kitchen with a gas cooker and foodstuffs kept on shelves. By day, the family sits around a stove to keep warm and at night they lay the mattresses on the ground. But there are not enough to go around and the space is limited. So some of us "sleep sitting up", Sallat said. Like Abu Jabber and others, he said he fled to Kafr Lusin for safety because border regions are usually spared bombardments. He said that if forced, he would "enter Turkey". "Look how life is beautiful behind the wall, while here it's a disaster," he said. "Aren't we humans too? If we have to … we will tear down the wall."