MONROVIA- The US and UN leaders on Monday called for "more robust" international efforts to tackle Ebola, after medics in Liberia demanded danger money to treat patients in what officials termed the worst health crisis of modern times.

The call from US President Barack Obama and UN Secretary General Ban Ki-moon came as doctors and nurses in Liberia, one of the worst-hit countries, went on strike to demand higher pay to care for Ebola patients there.

Health care workers in west Africa are on the front line of the Ebola outbreak -- branded by the World Health Organization as "the most severe acute public health emergency in modern times".

The epidemic has killed more than 4,000 people this year, mostly in Guinea, Sierra Leone and Liberia.

The Liberian walkout came as Obama spoke with Ban about the need for greater international efforts to fight the epidemic, with at least two cases of contamination reported beyond west Africa, in the US and Europe.

The two leaders called for "more robust commitments and rapid delivery of assistance by the international community", the White House said in a statement.

"Both leaders agreed that, given the threat posed by Ebola, at this crucial juncture members of the international community must redouble their resolve and commitment," the statement said.

The president also called on member states to "support the UN appeal and to provide the personnel, equipment and supplies required to stop the epidemic at its source."

Obama and his French counterpart Francois Hollande also issued a joint call for "stepped-up" global efforts to combat the disease.

SOURCE: AFP