Rising insecurity in Nigeria"s northwestern state of Zamfara has spawned a humanitarian crisis, International aid group Medicins Sans Frontieres (MSF) said on Thursday. Gunmen, often riding motorcycles, have attacked towns in the northwest in recent years, forcing thousands to flee across the northern border to Niger. Attackers have attained global notoriety through mass kidnappings at schools, abducting more than 800 students since December. MSF, also known as Doctors Without Borders, said the security situation had worsened in the last few months. It referred to an increase in reports of kidnappings, killings, armed robbery and sexual violence in the region. The medical group said its teams in Zamfara, one of the states worst hit by the violence, treated 10,300 children in the first four months of 2021 for ailments including severe malnutrition, measles, and respiratory infections. It said the number of children treated was 54% higher than in the same period last year. "Our teams in Zamfara state have witnessed an alarming rise in preventable illnesses associated with a lack of food, drinking water, shelter and vaccinations," said MSF doctor Godwin Emudanohwo. Rising violent crime in the northwest has compounded the challenges faced by Nigeria in northern states which are typically poorer than those in the south of Africa"s most populous country of about 210 million. A decade-old Islamist insurgency in the northeast has killed more than 30,000 people and forced at least 2 million to flee their homes, creating one of the worst humanitarian crises in the world.