Kenya is closing its borders to travellers from Guinea, Liberia and Sierra Leone, the three countries worst hit by the Ebola outbreak, the government has announced.

Kenya Airways also announced that it would suspend its flights to Freetown and Monrovia when the government travel ban on passengers comes into effect on Wednesday.

Several European carriers have already suspended services to the Sierra Leonean and Liberian capitals, where states of emergency have been declared to try to slow the spread of the disease.

Kenyan Health Minister James Macharia said the measure was also aimed at travellers who have passed through the affected countries.

"In the interest of public health the government has decided to temporarily suspend entry into Kenya of passengers travelling from or through the three West African countries affected by Ebola, namely Sierra Leone, Guinea and Liberia," he said.

The measure does not affect health workers fighting the epidemic, Macharia said, nor Kenyans returning home from the three countries.

However, he warned that both groups would be subject to "strict checks... and it may be necessary to put people in quarantine".

The move comes amid an international appeal to help contain the deadly virus, which has already killed 1,145 people across West Africa this year.

Volunteers trained

Meanwhile, Nigeria said it had trained 800 volunteers to help in the fight against Ebola as the country's already weak healthcare system struggled to cope with the outbreak.

Authorities in Lagos, where four people have died from the virus, last week appealed for volunteers to make up for a shortage of medical personnel because of a six-week doctors' strike over pay.

"People have heeded our call for service", said Hakeem Bello, a spokesman for Lagos State Governor Babatunde Fashola.

"We have trained some 800 volunteers in the area of contact tracing, sensitisation and treatment of the Ebola disease", he added.

Experts say Ebola is raging out of control in the region, with the World Health Organization 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, with charities and health authorities battling to keep it from spreading.

"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 Kailahun told AFP news agency.

But officials fear an outbreak in the key regional hub of Nigeria could be far more dangerous, and US health authorities pledged this month to send extra personnel and resources.

Lagos' state government 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.

Nigerian doctors have been on a nationwide strike since July 1 to demand a pay rise and better working conditions.