The Philippines on Thursday urged hundreds of its citizens to leave Ebola-hit west African nations, as it announced anyone who returned would be placed under a 21-day quarantine.

Foreign Affairs Secretary Albert del Rosario said the government had made a "voluntary repatriation" call to about 900 workers in Liberia, Guinea and Sierra Leone.

He told local television network ABS-CBN that President Benigno Aquino had also ordered those who did return would have to be isolated in a government facility.

"The president has asked us to come down with a ruling, anyone coming from those countries, they must undergo a 21-day quarantine," del Rosario said.

With 10 million Filipinos working abroad, the country is "very vulnerable" amid the outbreak of the killer disease, del Rosario said.

More than 100 Filipino peacekeepers who will be pulled from Liberia next month because of Ebola fears will also be quarantined in a military facility, health department spokesman Lyndon Lee Suy told AFP.

Some US authorities have recently ordered quarantines, which have proved highly controversial amid concerns over potential human rights violations and whether they could have unintended, harmful consequences.

The health department this week started training 130 doctors, nurses and medical workers from government hospitals to handle possible Ebola cases.

Close to 300 others from private hospitals and local government offices will be trained in the coming weeks, according to Lee Suy.

At least 20 government hospitals were designated as Ebola referral and treatment centres, including three in the capital, Lee Suy said.

An entire hospital in the southern suburbs that specialises in infectious diseases and animal bites may be designated as an Ebola centre should there be a large number of infections, he said.

"We can't say whether or not we're prepared because that's subjective, but we are in a better position to address the problem," he said.

Before the president ordered forced quarantines, 126 Filipinos who returned home from the three west African countries were "monitored" by the health department from their homes, according to Lee Suy.

Twelve of the 126 developed fever within the 21-day quarantine period but later tested negative for Ebola, he said.

The Ebola outbreak that has been ravaging west Africa has claimed 4,922 lives, according to the World Health Organization.

The rate of infections in hard-hit Liberia appears to have slowed, the WHO said on Wednesday, but it warned the crisis was not over.