Doctors Without Borders (MSF) warned the crisis gripping Guinea, Liberia and Sierra Leone would only get worse and could not rule out it spreading to other countries.
The International Civil Aviation Organization (ICAO) has met global health officials on implementing measures to halt the spread of the disease, as the pan-African airline ASKY suspended all flights to and from the capitals of Liberia and Sierra Leone.
Meanwhile the European Union allocated an extra two million euros ($2.7 million) to fight the outbreak, bringing total EU funding to 3.9 million euros.
"The level of contamination on the ground is extremely worrying and we need to scale up our action before many more lives are lost," said EU Humanitarian Aid Commissioner Kristalina Georgieva.
The bloc has deployed experts on the ground to help victims and try to limit contagion but Georgieva called for a "sustained effort from the international community to help West Africa deal with this menace".
In Britain, Foreign Secretary Philip Hammond was to chair a meeting of the government's COBRA crisis management committee to assess the situation.
Prime Minister David Cameron "does regard it as a very serious threat", Hammond told Sky News television.
"We are very much focused on it as a new and emerging threat which we need to deal with."
One person in England has been tested for the disease but the test proved negative.
Bart Janssens, MSF's director of operations, warned there was no overarching vision of how to tackle the outbreak, in an interview with La Libre Belgique newspaper.
"This epidemic is unprecedented, absolutely out of control and the situation can only get worse, because it is still spreading, above all in Liberia and Sierra Leone, in some very important hotspots," he said.
"We are extremely worried by the turn of events, particularly in these two countries where there is a lack of visibility on the epidemic."
"If the situation does not improve fairly quickly, there is a real risk of new countries being affected."
"That is certainly not ruled out, but it is difficult to predict, because we have never known such an epidemic."
- Unstoppable bleeding -
Since March, there have been 1,201 cases of Ebola and 672 deaths in Guinea, Liberia and Sierra Leone, according to the US Centers for Disease Control and Prevention.
Ebola can kill victims within days, causing severe fever and muscle pain, vomiting, diarrhoea and, in some cases, organ failure and unstoppable bleeding.
"We are lacking an overarching view to understand where the chief problems are," said Janssens.
"It's up to the World Health Organization (WHO) and to government to to deploy and organise the capacity and effort required to start to control this epidemic."
Togo-based pan-African airline ASKY, which serves 20 destinations, said it halted all flights to and from Liberia and Sierra Leone following the death of a passenger from the virus after they had travelled from Liberia to Nigeria via the Togolese capital Lome.
The 40-year-old man died in Lagos on Friday in Nigeria's first confirmed death from Ebola.
The virus hitchhiking across borders for the first time aboard the pan-African airline could lead to new flight restrictions aimed at containing outbreaks, the world aviation agency said.
"Until now (the virus) had not impacted commercial aviation, but now we're affected," ICAO secretary general Raymond Benjamin said.
"We will have to act quickly."
A statement is expected to be published in the coming days on next steps.
British Airways said it was maintaining its flights to west Africa but would monitor the situation closely.
In Romania, the foreign affairs ministry warned citizens planning on travelling to west Africa to avoid affected areas.