Ban Ki-moon has launched another urgent appeal for funds to help fight Ebola after a United Nations drive for donations fell short of its target.

The UN chief said a $1bn trust fund he launched in September has received just $100,000 (£62,000) so far.

He joins a growing chorus of world leaders criticising the global effort to tackle the Ebola outbreak.

The disease has killed about 4,500 people so far, mostly in Liberia, Guinea and Sierra Leone.

Although several countries across the world have pledged to support the struggle to contain Ebola, few have matched their pledges with donations.

Donors have given almost $400m (£250m) to other UN agencies and aid organisations but the trust fund itself has received pledges of just $20m (£12m) and only Colombia has paid up so far.

The UN special envoy on Ebola, David Nabarro, said the fund was intended to offer "flexibility in responding to a crisis which every day brings new challenges".

"It allows the areas of greatest need to be identified and funds to be directed accordingly," he added.

Mr Ban said it was time for the countries "who really have capacity" to provide financial and other logistical support.

Similar calls have 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 by the deadly virus.

WHO official Isabelle Nuttall said 15 African countries are 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.

US reservists on standby

Meanwhile, President Obama has given the go-ahead for US military reservists to be deployed to West Africa if needed. They would join the 4,000 American troops already being sent to the region.

The president also said he was open to appointing someone to head the Ebola response in the US, a so-called czar.

Mr Obama's senior health advisors have met scathing criticism after two nurses became infected at a Texas hospital by a patient who later died.

US officials now believe one of the nurses, Amber Vinson, may have been sick and contagious for four days and flown on two flights before being diagnosed with the disease.

Disease control specialists are being sent to Ohio to help monitor people she came into contact when she flew there from Dallas last week.

Source: BBC