Nigerian President Goodluck Jonathan has declared the outbreak of Ebola "a national emergency" and approved more than $11m (£6.5m) to help contain it.
The move comes after the World Health Organization (WHO) said the spread of the virus in West Africa was an international health emergency.
WHO says 961 people have died from Ebola in West Africa this year, two of them in Nigeria.
The total number of cases stands at 1,779, the UN health agency said.
In a statement, President Jonathan called on Nigerians to report any suspected Ebola cases to the nearest medical authorities.
He also urged the public not to spread "false information about Ebola which can lead to mass hysteria".
Nigeria became the fourth West African country involved in the outbreak when a dual US-Liberian citizen infected with Ebola arrived in Lagos after flying from Liberia via Togo on 20 July.
He died five days later and eight people who came into contact with him were also later diagnosed with Ebola. One of them, a nurse, died on Tuesday.
Nigeria's state oil company said on Friday it had shut down one of its clinics in Lagos following a suspected case.
US health authorities said on Friday they were sending extra personnel and resources to Nigeria.
"We are starting to ramp up our staffing in Lagos," US Centers for Disease Control and Prevention spokesman Tom Skinner told AFP news agency.
"We are really concerned about Lagos and the potential for spread there, given the fact that Lagos - and Nigeria for that matter - has never seen Ebola."
International companies are also taking protective measures and the world's largest steelmaker, ArcelorMittal, says it has begun evacuating some workers at its iron ore mines in Liberia.
Guinea, Sierra Leone and Liberia have already declared varying levels of emergency over the spread of the virus.
WHO said on Friday that 68 new cases and 29 deaths were reported over the course of two days this week.
They included 26 new cases in Sierra Leone and 38 in Liberia, but no new cases in Guinea, where the outbreak began.
The agency said a co-ordinated response was essential to reverse the spread of the virus.
"The possible consequences of further international spread are particularly serious in view of the virulence of the virus," WHO said after a meeting on Friday.
The Ebola virus was first discovered in the Democratic Republic of Congo in 1976. Experts say this outbreak is unusual because it started in Guinea, which has never before been affected, and is spreading to urban areas.
Two US citizens infected with Ebola while working in West Africa are currently being treated at a hospital in Atlanta, Georgia.
Dr Kent Brantly said in a statement on Friday that he was getting better every day. The husband of aid worker Nancy Writebol said she also appears to be improving.
Both have been treated with an experimental drug.
Ebola virus disease (EVD)
- Symptoms include high fever, bleeding and central nervous system damage
- Fatality rate can reach 90% - but the current outbreak is about 55%
- Incubation period is two to 21 days
- There is no vaccine or cure
- Supportive care such as rehydrating patients who have diarrhoea and vomiting can help recovery
- Fruit bats are considered to be virus' natural host