Freetown (AFP) - Sierra Leone began a second 42-day countdown to becoming Ebola-free on Sunday as it discharged its last two known patients and lifted its quarantine restrictions in the north, local health officials said.

"The last two Ebola patients were discharged from the Mathene Treatment Centre in the northern city of Makeni, after their tests proved negative," a statement from the Bombali District Ebola Response Centre said.

No details were given on the patients, but the statement added that around 1,500 people confined to their homes following outbreaks in the northern Bombali district and neighbouring Kambia had been released.

President Ernest Bai Koroma had hailed "the beginning of the end of Ebola in Sierra Leone" as Adama Sankoh, 34, was released from hospital in Makeni, the country's third-largest city, on August 24.

But hopes that the outbreak was beaten were dashed just days later when a 67-year-old woman died in Kambia, followed by a 16-year-old girl in Bombali two weeks later.

The World Health Organization says a country can be declared Ebola-free 42 days after the last confirmed case has tested negative twice for the virus, once after each 21-day maximum incubation period.

The National Ebola Response Centre in Freetown welcomed the development, but issued a statement calling for a missing contact of an Ebola patient in Kambia, regarded as "high risk", to turn herself in.

"She is not a criminal but we want her to give herself up so that we can check her status," spokesman Sidi Yahya Tunis said of the woman, who disappeared 28 days ago.

Since first emerging in December 2013, the worst outbreak of Ebola in history has infected 28,000 people and left some 11,300 dead -- almost all in Sierra Leone, Liberia and Guinea.

But with Liberia declared free of transmission, and Guinea recording just three cases in September, life is returning to normal in all three countries.