A national immunization campaign for much more than 4 million children in the north of the war-torn country was initiated by Yemen's health officials on Saturday.

The World Health Organization, UNICEF and other international aid organizations are supporting the three-day campaign, the local health departments said in a comment.

Door-to-door vaccination is directed at children below the age of five.

Since late 2014, when the Iran-backed Houthi group took over control of many northern provinces and obligated the globally renowned government of President Abd-Rabbu Mansour out of the capital of Sanaa, Yemen has been entangled in civil war. 

The tensions managed to bring starvation to the underprivileged Arab nation and caused repetitive flare ups of fatal pandemics such as cholera and polio.