SANAA, May 12 (Xinhua) -- The World Health Organization (WHO) said on Saturday that the diphtheria outbreak has killed at least 91 people in war-torn Yemen since late October.

A total of 1,725 suspected cases of diphtheria have been recorded in 20 of Yemen's 23 provinces, compared to 1,516 suspected diphtheria cases with 84 associated deaths reported on April 3.

Diphtheria, which spreads through sneezing caused by a common cold, has mainly infected children in Yemen.

Also in the day, a UN-backed national campaign for immunizing children against diphtheria was launched.

In March, the WHO, the UN International Children's Emergency Fund (UNICEF) and Yemen's health authorities launched a large-scale vaccination campaign across the country to combat the disease.

The impoverished Arab country has been locked into a civil war since Iran-backed Shiite Houthi rebels overran much of the country militarily and seized all northern provinces including the capital Sanaa in 2014.

Saudi Arabia has been leading an Arab military intervention coalition in Yemen since 2015 to support the government of President Abd-Rabbu Mansour Hadi after Houthi rebels forced him into exile.

The UN has listed Yemen as the country of the world's most serious humanitarian crisis, where 7 million Yemenis are on the brink of famine, and cholera has caused more than 2,000 deaths.