The Ebola outbreak that has left more than 660 people dead across West Africa has spread to Nigeria.

The disease has spread to Africa's after a Liberian man with a high fever vomited aboard an aeroplane to Nigeria and then died there, officials said.

The 40-year-old man had recently lost his sister to Ebola in Liberia, health officials there said.

It was not immediately clear how he managed to board a flight, but he was moved into an isolation ward upon arrival in Nigeria on Tuesday and died yesterday.

Nigerian health minister Onyebuchi Chukwu said it was the first case of Ebola to be confirmed in Nigeria since the current outbreak emerged this year. The disease already has hit Guinea, Liberia and Sierra Leone.

"All ports of entry into Nigeria, including airports, seaports and land borders, are placed on red alert," he said.

"Ministry of health specialists have been positioned in all entry points. Active surveillance has also been stepped up."

Authorities are investigating anyone who may have come into contact with the deceased, Mr Chukwu said.

"We have already gotten in touch with all the passengers," he said. "We are monitoring and investigating."

Liberia's chief medical officer Bernice Dahn identified the Ebola victim as a government official with the finance ministry.

"When his sister died, his workmates were kind of afraid for him to be around," she said. "We received several calls from workmates on whether it was advisable for him to go to work."

The man told health officials that he had not had any physical contact with his sister, and based on his explanation, he initially was told to report back to work but was advised not to travel.

He later was asked to stay home for 21 days but apparently continued working.

He flew to Nigeria to attend an international conference. Blood tests for Ebola returned positive from the Lagos University Teaching Hospital.

Ebola, one of the world's most deadly and contagious diseases, has now infected at least 1,093 people in Sierra Leone, Liberia, Guinea, and now Nigeria, according to the World Health Organisation.