The situation was "deteriorating faster, and moving faster, than we can respond to", BBC quoted MSF President Joanne Liu as speaking in Geneva.
Earlier, the World Health Organisation (WHO) said the scale of the outbreak appeared to be "vastly underestimated". It said that "extraordinary measures" were needed.
The epidemic began in Guinea in February and has since spread to Liberia, Sierra Leone and Nigeria. Ebola has so far claimed over 1000 lives in West Africa alone.