Liberian President Ellen Johnson Sirleaf on Thursday vowed to crack down on those responsible for a rise in ritual killings in the West African country as it seeks to emerge from the shadow of an Ebola epidemic.

In some areas of central Africa, body parts are prized for their supernatural powers and are used in black magic ceremonies. Local media have reported at least 10 related murders in Liberia since the summer.

"We are witnessing the rise in what appears to be ritualistic killings and armed robbery in the country, thus threatening our security," Johnson Sirleaf said in a speech Thursday.

"I am instructing the security forces to rigorously enforce the law to the letter and bring this ugly situation under immediate control," she added.

It is not yet clear why ritual killings are rising and Johnson Sirleaf offered no explanation. But some residents have speculated that presidential hopefuls seeking to replace Johnson Sirleaf when her final term expires 2017 are using black magic to boost their chances.

Liberia was declared Ebola-free for the second time in September after reporting more than 4,800 deaths but its economy is struggling to recover.

Johnson Sirleaf said in the same speech she would seek to boost power supply and access to electricity and build additional infrastructure in the last two years of her term.