Sierra Leone has restricted travel in three more Ebola hotspots where more than a million people live, meaning about a third of the country's population is under quarantine.
Sierra Leone is one of the hardest hit countries in the outbreak sweeping West Africa that is believed to have killed more than 2,900 people, according to new World Health Organisation (WHO) figures. The agency says the situation in the country continues to deteriorate, driven primarily by a sharp increase of cases in the capital Freetown.
In an address to the nation, president Ernest Bai Koroma put the Port Loko, Bombali and Moyamba districts under isolation, allowing only people delivering essential services to enter and circulate.
The WHO also noted that these districts were seeing a rise in cases.
In other parts of Sierra Leone, including the capital, homes will be put under quarantine when cases are identified, a government statement after the address said.
The Ebola outbreak, the largest ever, has also hit Liberia and Guinea and is believed to have infected more than 6,200 people. A patient also slipped into Senegal from Guinea but the disease does not appear to have spread there.
Nigeria has linked 20 cases to the disease and eight deaths after a man infected with Ebola traveled there from Liberia, but the outbreak seems to have been contained.
President Goodluck Jonathan said: "Nigeria is free of the virus now but we know that to be permanently free from it, we must remain vigilant and work with WHO and the international community to eradicate it completely from our sub-region and forestall the possibility of its re-emergence on our shores through migration."
The outbreak's unprecedented scale and geographic spread have pushed governments to impose severe measures, like the cordoning off of entire towns or regions. Last week, Sierra Leone imposed a three-day nationwide lockdown, confining its six million people to their homes while health teams spread out to look for the sick and educate people about the disease.
That exercise revealed that the outbreak is worse than thought, the government said, with 160 cases found during the shutdown.
"There is a desperate need to step up our response to this dreaded disease," the government statement said. "The prognosis is that without additional interventions or changes in community behaviour, the numbers will increase exponentially and the situation will rapidly deteriorate."
Two districts near the outbreak's epicentre - Kenema and Kailahun - had already been isolated. In all, the movement of more than two million people is now restricted. Liberia, the country hardest-hit by the disease, cordoned off areas of its capital at one point to slow transmission.
The outbreak has overwhelmed the weak health systems of some of the world's poorest countries. There are not enough doctors and nurses or even clinics to treat the spiralling number of cases.
The five countries have about 900 beds that can be used to treat Ebola patients, and more than 700 more are on their way. But the WHO warned that will still leave a shortfall of more than 2,100 beds. Liberia alone needs 1,500 more than are currently being set up.