International medical charity, Medecins Sans Frontieres (MSF), has condemned the killing of Hassan Muhammad, one of its nurses in Zamfara state, in the north-west of Nigeria.
The nurse was returning to his work station on Saturday when gunmen opened fire on the public vehicle he was travelling in.
Two other people, the driver of the vehicle and a passenger, also died in the attack.
MSF said it was shocked and saddened by the death of the 37-year-old nurse who worked in Shinkafi town, where its team runs a facility at the local hospital.
The Zamfara state has seen an upsurge in violence where gangs have carried out mass kidnappings of students, attacked villages and people traveling by road, for ransom.