Sierra Leone plans a three-day nationwide lockdown in an effort to halt an Ebola outbreak that has killed hundreds, a move that a leading medical charity said Saturday will not help.

People will not be allowed to leave their homes for three days under the plan, set to start September 19. The lockdown is being billed as a predominantly social campaign rather than a medical one, in which volunteers will go door-to-door to talk to people.

"We believe this the best way for now to identify those who are sick and remove them from those who are well," said Alhaji Alpha Kanu, Sierra Leone's minister of information and communication.

But Médecins Sans Frontières, also known as Doctors Without Borders, said such a lockdown is unlikely to stop the spread of the disease.

"Large scale coercive measures like forced quarantines and lockdowns are driving people underground and jeopardizing the trust between people and health providers. This is leading to the concealment of cases and is pushing the sick away from health systems," the charity group said in a statement.

"This is leading to the concealment of potential cases and is pushing the sick away from health systems."

It's not the first time a quarantine or lockdown has been tried. In August, the Liberian government locked down one of the poorest neighborhoods in the capital of Monrovia in an attempt to stop the spread of the virus. The move resulted in riots.

Sierra Leone set the lockdown date for September 19-21 to give the country time to train volunteers and get needed equipment, such as ambulances, Kanu said.

During the lockdown, 21,000 volunteers will fan out across the nation to talk with people about how to protect themselves from the disease, as well as identify Ebola cases, Kanu said.

(CNN)