A two-week lockdown on the eastern diamond mining district of Kono was imposed on Wednesday after eight cases of Ebola were confirmed in one day.
According to Sierra Leone's health ministry, Tuesday's spate of Ebola reports increased the cumulative total of confirmed cases in the region to 119.
The lockdown will limit residents' movements until December 23.
Sierra Leone, along with Guinean and Liberia, is at the epicentre of the worst Ebola outbreak on record. The virus has claimed over 6,300 lives in west Africa over the past year, including more than 1,700 in Sierra Leone.
Officials from the World Health Organization (WHO) and US Center for Disease Control have been assisting Sierra Leone's National Ebola Response Center to prevent the virus from spreading throughout Kono and its population of 350,000.
"Our team met heroic doctors and nurses at their wits' end, exhausted burial teams and lab techs, all doing the best they could but they simply ran out of resources and were overrun with gravely ill people," said WHO's national Ebola coordinator Olu Olushayo.
The decision to impose a lockdown was taken at a meeting of traditional rulers known as the Council of Paramount Chiefs, its chairman Paul Saquee told reporters.
"The decision is a follow-up to the high increase in positive Ebola cases that have engulfed the district," Saquee said.
Although rapid reaction has helped contain the virus to about half of the 15 chiefdoms in Kono, WHO teams that arrived in the area 10 days ago were taken aback at the situation they encountered.
In the space of 11 days, two WHO teams buried 87 victims, including a nurse and an ambulance driver enlisted to help dispose of corpses piling up in the local hospital.
- Empty markets -
Doctor Amara Jambai, the Ministry of Health and Sanitation's Director of Disease Prevention and Control, used a local saying to describe the dramatic surge in Kono's Ebola cases.
"We are only seeing the ears of the hippo," Jambai said.
Despite the concerns however locals were said to be reacting calmly, according to journalists reached by phone by AFP.
Freelance journalist Emmanuel Lebbie said: "People are moving freely within towns and villages, but are not allowed to go beyond the district itself."
Most people were remaining indoors and while shops were open, the markets were largely empty of consumers.
Only essential vehicles such as fuel-carrying tankers, military, police, NGO workers and UN-associated vehicles were allowed through heavily monitored checkpoints into the district.
Private and commercial vehicles and motor cycle taxis are barred, and mining activity has ceased, one mines monitor reported.
Residents expressed mixed reaction to lockdown.
"We are happy about the response," said cocoa farmer Steve Boima. "If that's what it takes to kick Ebola out of the district, I am for it."
But Thomas Lahai, an unemployed motor mechanic, said things could have gone more smoothly.
"Although I support the action, it was not widely publicized and when the word got round (Tuesday), it resulted in panic buying with the result that some essential foodstuffs like yam, pepper and fish sold out at exorbitant prices."
Earlier this year, Sierra Leone quarantined hundreds of thousands of people, sealing off districts across the country in a bid to combat the Ebola outbreak.