No details were given on the death's links to the newly confirmed case.
Previously the disease was suspected in patients only in rural parts of the country, but reaching the city of Mbandaka makes the outbreak, which was first reported on May 8, significantly bigger than previously thought.
"WHO and our partners are taking decisive action to stop further spread of the virus", he added.
The organization is working with health NGO Medecins Sans Frontières (MSF) and other partners to boost the number of special isolation wards to treat patients.
United Nations mulls worldwide war crimes probe of Gaza killings
Mideast envoy Nikolay Mladenov to help deter violence, protect civilians, and create "an environment conducive to dialogue". Protests began after the United States embassy was officially opened in Jerusalem on Monday (local time).
It raised its view of the risks after a case of Ebola was confirmed in the city of Mbandaka, which the agency said was "a large urban centre located on major national and worldwide river, road and domestic air routes".
"The remote location of the outbreak hampers both the information about the outbreak and interventions to control it", said Cyrus Shahpar, director of epidemic prevention at Resolve to Save Lives, a New York-based organisation. This is the first urban case in the latest outbreak and is being considered to be one of the most serious ones in recent times.
Later on Friday, the WHO will convene an Emergency Committee of experts to advise on the global response to the outbreak, and decide whether it constitutes a "public health emergency of worldwide concern".
Earlier, the world health organization sent to the Democratic Republic of the Congo, more than 5 thousand doses of an experimental vaccine against Ebola.
The WHO revised its assessment of the risk of spread of the epidemic to "very high" at the national level and "high" for neighbouring countries.
Storms slam US Northeast, snarling transport and causing power outages
Two people died and thousands of homes and businesses were without power after strong storms pounded the Northeast on Tuesday. In Connecticut , the state's two major utilities reported 90,000 without electricity, most in the western part of the state.
Front-line health workers, people who have been in contact with those infected and contacts of those contacts will receive the Ebola vaccine, according to the WHO. The last major outbreaks have affected people across West Africa between 2014 and 2016.
Notably, about 23 people have reportedly died and 42 people have contracted the virus since Epola outbreak began earlier in May.
The European Commission has announced a package of urgent humanitarian aid to help contain an outbreak of Ebola in the Democratic Republic of Congo.
Ebola is lethal and highly contagious, which makes it hard to contain - especially in urban environments where people are mobile and come into more contact with others. Humans can also be exposed to the virus, for example, by butchering infected animals.
WHO spokesman Tarik Jasarevic said on Friday that Congo's Ministry of Health had provided updated figures: 45 cases overall since April 4, including 14 confirmed, 10 suspected and 21 probable.
Jets' 2nd period momentum short-lived in 4-2 loss to Knights
Defensively, the Vegas Golden Knights are allowing 2.7 goals per game and are killing 81.4 percent of their opponents power plays. It was a big emphasis. "Like we need an excuse to come to Vegas!" "They were obviously important at a key time for us".