These are medical units that fall under the protections of the red cross as outlined in the Geneva Conventions.
"Under the Geneva Conventions, the three distinctive emblems of the red cross, red crescent and red crystal are intended to identify and protect medical and relief workers, military and civilian medical facilities, mobile units and hospital ships during armed conflict."
https://www.redcross.org/content/dam/redcross/atg/PDF_s/Inte... (PDF)