MANILA (AFP) - The Philippines said Friday people arriving from west African countries hit by the Ebola outbreak would be monitored for a month to prevent the virus spreading to the Asian nation.

Manila last month imposed a ban on travel to Guinea, Liberia and Sierra Leone amid the world's worst ever outbreak of the tropical virus, while the health ministry announced extra measures on Friday.

"We have to be proactive. We know that the threat is there, and we do not want any surprises," health ministry spokesman Lyndon Leesuy told a news conference.

Filipinos returning from the three outbreak countries, as well as visitors from those nations, would be screened at Philippine airports and their health status monitored daily for a month after their arrival, he added.

The health ministry said 20 Filipino workers who returned from Sierra Leone in June and July were put under this regime by health officials.

Hospital facilities have been prepared to admit any who would develop Ebola symptoms, it said in a statement, while stressing the country remained free of the deadly virus.

The foreign department said there were 3,491 Filipinos working in Guinea, Liberia and Sierra Leone when the travel ban was imposed on July 4.

They are among an estimated 10 million Filipinos who work abroad.

The three west African countries are struggling to contain an epidemic that has infected more than 1,300 people since the start of the year, hit major cities and sparked alarm over its possible spread to other nations.

The World Health Organization said the death toll had risen by 57 to 729 on Thursday, announcing that 122 new cases had been detected between Thursday and Sunday last week.