A UN medical official who caught Ebola while working in Liberia has died in a hospital in Germany, the clinic in Leipzig said on Tuesday.

The 56-year-old Sudanese man, who has not been named, arrived at the centre last week and was the third Ebola patient to be treated in the country. He died in the St. Georg hospital in the early hours of Tuesday morning.

"The patient sick with Ebola fever died during the night in St. Georg Clinic in Leipzig. Despite intensive medical measures and maximum efforts by the medical team, the 56-year-old UN employee succumbed to the serious infectious disease," the hospital said in a statement.

The man had been working as a UN medical official in Liberia, where the virus has been identified in 14 of 15 counties.

The German newspaper Der Spiegel reported that one patient is still receiving treatment as a Frankfurt hospital, while a third was released from a Hamburg clinic after five weeks of successful treatment.

The outbreak has killed more than 4,000 people since March, with the majority of deaths occuring in Liberia, Sierra Leone, Guinea and Nigeria. It is the worst outbreak of the virus since it was discovered in 1976.

The World Health Organisation described the outbreak as the "most severe, acute health emergency seen in modern times".

It was announced that scanning for the virus would begin in London's Heathrow airport this morning.