The death toll, which passed the 1,000-mark at the weekend, soared higher between August 10 and 11.
The number of confirmed infections jumped by 128 over the two days, bringing the total number of cases to 1,975 people, the UN's health agency said.
New cases and deaths had been registered in all four west African countries so far hit by the worst Ebola epidemic seen since the deadly virus was discovered four decades ago.
Liberia saw 71 new cases and 32 new deaths, while Sierra Leone recorded 53 new cases and 19 more deaths, according to fresh WHO data.
Nigeria, meanwhile, counted one more death, bringing the total there to three, but WHO lowered the total number of suspected, probable and confirmed cases in the country to 12 from 13.