A top Guinea health official said Sunday that the country has plunged into an Ebola "epidemic situation" with seven cases confirmed in the West African nation, including three deaths.
"Very early this morning, the Conakry laboratory confirmed the presence of the Ebola virus," Sakoba Keita said after an emergency meeting in the capital.
Health Minister Remy Lamah had earlier spoken of four deaths. It was not immediately clear why the new toll was lower.
The cases marked the first known resurgence of Ebola in West Africa since a 2013-2016 epidemic that began in Guinea and killed more than 11,300 people across the region.
The virus was first identified in 1976 in Zaire, now the Democratic Republic of Congo (DR Congo).
A World Health Organization (WHO) representative in Conakry said the agency would send help quickly.
Keita, head of the National Agency for Health Security, said one person had died in late January in Gouecke, southeastern Guinea, near the Liberian border.
The victim was buried on February 1 "and some people who took part in this funeral began to have symptoms of diarrhoea, vomiting, bleeding and fever a few days later," he said.
Samples tested by a laboratory set up by the European Union in Gueckedou, located in the same region, revealed the presence of the Ebola virus in some of them on Friday, said Keita.
He added that with a total of seven cases and three deaths, Guinea was now in an "Ebola epidemic situation."
WHO representative Alfred George Ki-Zerbo told a press briefing: "We are going to rapidly deploy crucial assets to help Guinea, which already has considerable experience" treating the disease.
"The arsenal is stronger now and we will take advantage of that to contain this situation as fast as possible.
"The WHO is on full alert and is in contact with the manufacturer (of a vaccine) to ensure the necessary doses are made available as quickly as possible to help fight back," he added.
The WHO has eyed each new Ebola outbreak since 2016 with great concern, treating the most recent one in the DR Congo as an international health emergency.
In Guinea's neighbour Liberia, President George Weah put the country's health authorities on heightened alert Sunday.
Weah "has mandated the Liberian health authorities and related stakeholders in the sector to heighten the country's surveillance and preventative activities," his office said in a statement.
No cases of Ebola had been detected in Liberia so far however, it added.
"The president's instruction is intended to ensure Liberia acts proactively to avoid any epidemic situation, the kind Liberia witnessed in 2014."
Weah also told health authorities "to immediately engage communities in towns and villages bordering Guinea and increase anti-Ebola measures," the statement said.
DR Congo has faced several outbreaks of the illness, with the WHO on Thursday confirming a resurgence three months after authorities declared the end of the country's latest outbreak.
The country had declared the six-month epidemic over in November. It was the country's eleventh Ebola outbreak, claiming 55 lives out of 130 cases.
The widespread use of vaccinations, which were administered to more than 40,000 people, helped curb the disease there, however.
The 2013-2016 outbreak sped up the development of a vaccine against Ebola, with a global emergency stockpile of 500,000 doses planned to respond quickly to future outbreaks, the vaccine alliance Gavi said in January.