Sierra Leonean authorities said on Tuesday than Khan had died from the virus while being treated at a Doctors Without Borders (MSF) clinic in the far north of the country.

Three nurses who also worked at the main treatment center in Kenema, around 320 kilometers (200 miles) east of the capital Freetown had previously died of the disease, which in its final stages causes haemorrhaging.

Health Minister Miatta Kargbo called Khan a "national hero" and praised his "tremendous sacrifice" in working to save the lives of others.

Since March, the outbreak has killed more than 670 people in Sierra Leone, Liberia and Guinea. It has no specific treatment and a fatality rate of at least 60 percent.

A prominent Liberian doctor Samuel Brisbane died of Ebola last Saturday after treating patients in Monrovia.

WHO approaches Hamburg medics

Medical officials in the German city of Hamburg said Tuesday that the World Health Organization (WHO) had asked whether the city's university clinic could treat two infected medics from western Africa.

Leading virologist at Hamburg's Bernhard Nocht Institute, Professor Stefan Günther, said the treatment, if approved, would be a "psychological signal" to those medics trying to stem Ebola in Africa.

Currently hospitalized with Ebola in Liberia are two American medics -- Texas-trained missionary doctor Kent Brantly and co-worker Nancy Writebol.

West African airline suspends flights

The regional west African airline ASky said on Tuesday that it had suspended all of its flights to and from Freetown and Monrovia, the capitals of Sierra Leone and Liberia, to inhibit the virus' potential spread.

Passengers departing Conakry in Guinea and Lome in Togo were being screened by medical teams, ASky said.

Nigeria said it had banned entry to ASky until it could prove that all its passengers had been adequately screened. And, the private clinic where the man died was being "decontaminated."

WHO awaits lab results

The World Health Organization (WHO) said it was awaiting laboratory confirmation after Nigeria attributed Friday's death in Abuja of a Liberian finance ministry official to Ebola.

Patrick Sawyer, a naturalized American, who had flown with airline from Liberia to Nigeria, had intended to travel on to his home in the US state of Minnesota. His flight had stopped in Lome, Togo, en route to Lagos.

Lagos state's health commissioner, Jide Idris, said 59 people had been identified as potentially having contact with Sawyer, including airline employees.

Tackle source, says WHO

WHO spokesman Gregory Hartl urged western African nations to "put the necessary measures in place at the source of infection." So far, the WHO has avoided issuing warnings to restrict travel.

Contagion requires direct contact with secretions of a patient. Flu-like symptoms, including vomiting, can take 21 days to appear, according to the WHO.

Appeal from Plan International

The children's aid organization Plan urged to the international community on Tuesday to stop the virus' spread. A joint approach was needed "before it is too late," said Plan's catastrophe expert Unni Krishnan.

A spokeswoman for the Red Cross in Africa, Katherine Mueller, said while visiting Sierra Leone the greatest problem was to persuade residents to overcome their disbelief. Many denied Ebola's existence and turned instead to traditional healers.

Since its discovery in 1976, Ebola had been limited to remote corners of Congo and Uganda, until March when it emerged in Guinea.

ipj/kms (dpa, Reuters, AP, epd)