HONG KONG (AFP) - Hong Kong said on Wednesday it was quarantining all people from Guinea, Sierra Leone and Liberia who were showing Ebola-like symptoms on arrival in the city, as fears grow worldwide about the spread of the deadly virus.

Ebola has so far killed 670 people in the three west African countries, with 1,200 cases reported there and another in Nigeria, and the European Union is increasingly anxious that the outbreak could reach Europe.

Hong Kong, a densely populated city of some seven million people, is particularly alert to the spread of viruses after severe acute respiratory syndrome (Sars) killed almost 300 people eleven years ago.

Local media reports in the southern Chinese city on Wednesday said that a woman who had visited Kenya had briefly been quarantined on her return to Hong Kong.

The South China Morning Post, citing an unnamed hospital source, said the woman had travelled to Kenya for a 17-day holiday and was briefly quarantined when she arrived back.

A health official confirmed to AFP that a woman showing symptoms, including fever and vomiting, had tested negative for Ebola after returning from Africa.

Mr Dominic Tsang, chief infection control officer for the city's hospital authority, did not say where in Africa the woman had travelled from but insisted it was neither Guinea, Sierra Leone nor Liberia.

"As of today the fever had subsided and she is stable. She doesn't fall into the criteria (of a suspected Ebola case). She was discharged earlier today," Mr Tsang said.

Hong Kong is extremely cautious and wary about the spread of viruses since Sars swept through the city in 2003, killing 299 people and infecting around 1,800.

A government spokesman told AFP the stance taken towards travellers from Guinea, Sierra Leone and Liberia were "contingency measures" announced in response to fears about Ebola.

Ms Chuang Shuk-kwan, of the Centre for Health Protection, said: "The reporting criteria is quite simple.

"Any person who travelled from (those) three places to Hong Kong within 21 days who developed fever should be referred to the Hospital Authorities' infectious disease centre.

"(We) hope to contain every possible case," she added.

Fears that the Ebola outbreak could spread to Europe grew on Wednesday, with the EU allocating extra spending and leading medical charity Doctors Without Borders warning the epidemic was out of control.