The west African nation, which has registered some 3,400 deaths in the nine months since the outbreak spread from neighbouring Guinea, had seen a steady decline in new cases over recent months.
But it has warned that the trend was being threatened by people flouting a ban on traditional funeral rites, seen as a key factor in the spread of the highly infectious virus.
Palo Conteh, head of the government's National Ebola Response Centre, told reporters in the capital Freetown that the daily count of infections had risen to a peak of 16 so far this week.
In the previous week the daily tally had dropped as low as two, he said.
"We warned then against complacency and stated clearly that we must anticipate spikes in cases as we strive to get to zero. These numbers are rising because people continue to flout the law with impunity," Conteh added.
Ebola, one of the deadliest viruses known to man, is spread only through direct contact with the bodily fluids of the recently deceased or an infected person showing symptoms such as fever or vomiting.
Preventing unsafe burials has been a top priority in the response to the epidemic, yet the World Health Organization (WHO) says Sierra Leone reported 45 in a single week up to February 15.
Families of victims are supposed to inform the authorities, who ask Red Cross experts dressed in bio hazard suits and carrying disinfectant to bury the bodies.
Conteh said funeral homes had also reopened illegally across the country, accepting medical certificates as proof that the deceased were Ebola-free.
"Let me state that the safe medical and dignified burial policy still stands and I am sending a strong warning to all district medical officers, heads of hospitals and municipalities to desist from issuing certificates that permit people to embark on unsafe burials," he said.
The WHO said in its latest update today that, as of Sunday, 9,589 people had died of Ebola since the epidemic emerged in southern Guinea in December 2013.
Liberia has registered the highest death toll of 4,037 fatal cases while Sierra Leone has seen almost half of the total of 23,694 cases.

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