The fighting in Tripoli last month killed 376 people and wounded 1822, the WHO office in Libya said.
"The total number of people killed in April 2019 was 376 and 1822 wounded," the organization´s office said in a tweet published on its Twitter account on Wednesday.
The organization also renewed calls for an "immediate ceasefire".
No details were given on the number of civil and military casualties caused by the fighting.
The fighting between the forces of the internationally recognized National Reconciliation Government and that of Khalifa Khalifa Hafer is near the end of its first month.
On April 4, Marshal Hafer launched an offensive to take control of Tripoli.
Despite the fighting, especially south of Tripoli, neither side seems to have a clear ability to resolve the battle or make significant field progress in its favor.
The fighting has led to the displacement of some 45,000 people from the areas of clashes, Yousuf, the Minister of State for Displacement and Displaced Persons, said in the Al-Wefaq government.
The UN envoy to Libya, Maria de Valle Ribeiro, warned in an interview with Agence France-Presse of the "seriousness" of the humanitarian situation in Tripoli.
