Senegal has decided to toughen restrictions on travels from Ebola-hit West African countries as the newly appointed UN coordinator on the epidemic began his visit to countries affected by the deadly disease.

In a statement released late Thursday night, Senegal's interior ministry said the country has once again closed the land borders with neighboring Guinea, where hundreds of deaths from Ebola virus disease have been recorded.

Senegal sealed its borders with Guinea in March following a major Ebola outbreak before it re-opened them in May.

The interior ministry said the closure also extends to "air and sea borders for aircraft and ships from the Republic of Guinea, Sierra Leone and Liberia."

The ministry said relevant administrative functions and security forces will be tasked to strictly implement the new measures so as to prevent the virus from spreading into Senegal, where no Ebola cases have been found.

Meanwhile, David Nabarro, the newly-appointed chief coordinator in the UN system to battle the Ebola virus, on Thursday arrived in Monrovia, the capital of Liberia, on the first leg of his visit to the region to evaluate regional and UN responses to the challenge of Ebola.

Nabarro, a British public health expert, was appointed by UN Secretary-General Ban Ki-moon last week to serve as the senior UN system coordinator on Ebola virus.

He will also travel to three other countries affected by the Ebola outbreak -- Sierra Leone, Guinea and Nigeria, before returning to Geneva and New York to report to the UN on his findings.