More than 1,900 people have now died of Ebola in west Africa, the World Health Organization said Wednesday, warning the world's worst-ever outbreak of the virus is still gathering pace, Reuters reported.

"As of this week, we are reporting 3,500 cases confirmed in Guinea, Sierra Leone and Liberia and more than 1,900 deaths -- and the outbreak is rising," WHO chief Margaret Chan told reporters in Washington.

The latest toll represents a significant increase from the 1,552 deaths and 3,069 cases reported by the Geneva-based organization just days ago.