Millions of doses of two experimental Ebola vaccines could be ready in 2015, the World Health Organisation (WHO) has said.

The WHO also announced that five more experimental vaccines will begin testing in March.

However, the agency warned it is not clear whether any of these will work against the deadly virus that has already killed more than 4,800 people this year.

Dr Marie-Paule Kieny, from the agency, said there could be millions of doses of an Ebola vaccine in 2015 if early tests prove that the two leading candidates are safe and effective.

If the early trials hint at success, larger trials testing the vaccines in West Africa could begin as soon as December, Dr Kieny said.

She said five other possible Ebola vaccines should start being tested in March.

Trials of the two most advanced vaccines - one developed by GlaxoSmithKline in co-operation with the US National Institute of Health, the other developed by the Canadian Public Health Agency - have already begun in the US, the UK and Mali.

"The vaccine is not the magic bullet. But when ready, they may be a good part of the effort to turn the tide of this epidemic," Dr Kieny said.

In an indication of how the rising spread of Ebola is upending many attempts to halt this year's outbreak, Dr Kieny admitted that plans were changing "week to week" as governments, health agencies and donor countries tried to speed up efforts to fight the deadly virus.