The International Committee of the Red Cross says a staff member was killed Saturday in southern Yemen.
"One of our colleagues was killed by an armed man in Taez city," Red Cross official Adnan Hizam said.
Security officials told the Associated Press that Hanna Lahoud of Lebanon was shot by the gunman who opened fire on a ICRC vehicle.
If was not immediately clear how many people were in the vehicle and if there were any more casualties.
More than two million people have become internally displaced in Yemen since March 2015. That is when a Saudi-led coalition began a bombing campaign against Houthi rebels in support of Yemen's government.
Yemen, the site of the world's largest humanitarian crisis, has more than 22 million people in need of humanitarian assistance. Aid agencies warn needs are increasing - fueled by the ongoing conflict, collapsing economy, lack of social services and livelihoods.