Liberia has had the largest number of deaths from the virus. Photo: VINO

Christopher Stokes of Medecins Sans Frontieres (MSF) said the disease was still out of control.

He said it was "ridiculous" that volunteers working for his charity were bearing the brunt of care in the worst-affected countries.

The disease has killed about 4,500 people so far, mostly in west Africa.

MSF runs about 700 out of the 1,000 beds available in treatment facilities Liberia, Sierra Leone and Guinea.

The BBC's Mark Doyle, at the UN Ebola logistics base in Ghana, says it is generally agreed that at least three times that number are needed and that the disease is still out of control.

Donors have given almost $400m to UN agencies and aid organisations, and there have been some high-profile offers of help from the international community, our correspondent says, for example the British army building a field hospital in Sierra Leone.

However, UN Secretary General Ban Ki-moon on Thursday made another urgent appeal for funds to help fight the disease, saying a $1bn trust fund he launched last month had received only $100,000.

Another NGO, Action Aid, said the outbreak had to be tackled at source in west Africa.

Its head of humanitarian response, Mike Noyes, said in a statement: "There remains an urgent demand in countries like Liberia and Sierra Leone for more doctors, nurses, medical supplies and support for preventative measures.

"It is vital the world increase its efforts in fighting the disease."

Mr Noyes added that the current Ebola outbreak had already claimed three times as many lives as all previous outbreaks.

Growing chorus

Calls for more aid have also been made in recent days by US President Barack Obama, UK PM David Cameron, and World Bank President Jim Yong Kim.

Former UN Secretary General Kofi Annan has told the BBC he was "bitterly disappointed" with the international community's response.

"If the crisis had hit some other region it probably would have been handled very differently," he said in an interview with BBC Newsnight.

"In fact when you look at the evolution of the crisis, the international community really woke up when the disease got to America and Europe."

The World Health Organization has said it is "ramping up" efforts to prevent Ebola spreading beyond the three countries most affected.

WHO official Isabelle Nuttall said 15 African countries were being prioritised for help in prevention and protection, with the four countries directly bordering the affected areas - Ivory Coast, Guinea Bissau, Mali and Senegal - getting the most attention.