Sierra Leone has warned it is a serious crime to shelter patients infected with the Ebola virus who are in hiding.

The Health Ministry said several patients had discharged themselves from hospital in Kenema district, the heart of the country's outbreak.

The World Health Organisation has called for "drastic action" to contain the Ebola outbreak in West Africa, which has killed almost 400 people. It is the largest outbreak in terms of cases, deaths and geographical spread and there have been more than 600 cases since the outbreak started four months ago.