Kenya has become the latest country to ban travellers from parts of Ebola-hit west Africa.
Its decision comes as Nigeria, the continent's most populous nation, scrambles to stop the disease spreading throughout the country.
Kenyan Health Minister James Macharia said on Saturday that the country is closing its borders to travellers from Guinea, Liberia and Sierra Leone - the nations most affected by the worst-ever Ebola outbreak.
National carrier Kenya Airways also said it would suspend its flights to the capital of Sierra Leone, Freetown, and the capital of Liberia, Monrovia, when the ban takes effect on Wednesday.
The move comes amid an international appeal to help contain the deadly virus, which has already killed 1145 people across west Africa this year.
In Spain, where a missionary priest died recently of Ebola after being infected in Liberia, another person was being tested for the disease and was placed in hospital isolation on Saturday.
Nigeria's Health Minister Onyebuchi Chukwu told reporters on Saturday that 12 Nigerians have so far tested positive for the virus, including four who have died, while 189 others are under surveillance in the city of Lagos and six in the southeastern town of Enugu.
He said five of the patients have almost fully recovered but added that an experimental drug, nano silver, intended to be administered to the patients was not approved by the National Health Research Ethics Committee.
He also said the first Nigerian to be diagnosed with Ebola virus, a female doctor, had been discharged.
Nigeria has trained 800 volunteers to help in the fight against Ebola following an appeal by authorities in Lagos for volunteers to make up for a shortage of medical personnel because of a six-week doctors' strike over pay.
Experts say Ebola is raging out of control in west Africa, with the World Health Organisation declaring the epidemic an international health emergency and appealing for global aid.
The disease erupted in the forested zone straddling the borders of Guinea, Sierra Leone and Liberia earlier this year and spread to Nigeria last month.
The districts of Kailahun and Kenema in eastern Sierra Leone have become the new epicentres of the outbreak.
"You cannot mess about here: this virus will kill you. One mistake, one wrong move, and you're dead - that's it," a senior aid worker in Sierra Leone told AFP.
But officials fear an outbreak in the key west African hub of Nigeria could be far more dangerous.
The government of Lagos, a Nigerian city of 5.2 million, has stepped up a media campaign to raise awareness of how to prevent the spread of the disease, including radio and television advertisements and public health announcements.
Medical charity Doctors Without Borders (MSF) on Friday warned Ebola is spreading faster than authorities can handle and could take six months to bring under control.
Travel restrictions have been imposed across west Africa and several airlines have cancelled flights to affected countries in a bid to stop it spreading beyond the region.
Nigeria has also withdrawn its athletes from the Youth Olympics in the Chinese city of Nanjing as a result of the outbreak.
The International Olympic Committee has barred athletes from Ebola-hit countries from competing in pool events and combat sports.
Ebola is spread by contact with an infected person's bodily fluids, such as sweat and blood, and no cure or vaccine is currently available.
The last days of a victim's life can be grim, characterised by agonising muscular pain, vomiting, diarrhoea and catastrophic haemorrhaging described as "bleeding out", as vital organs break down.
