"The casualties of this week's attack on a migrant centre in Tajoura are 53 dead and 130 injured, making the overall toll of the Tripoli conflict nearly 1,000 dead and more than 5,000 wounded," the WHO tweeted.
"The WHO urges a rapid and peaceful solution so that all people in Libya are safe from harm," it added.
The UN-recognized government of National Accord (GNA) in Tripoli blamed anti-government forces led by warlord Gen. Khalifa Haftar the leader of the opposition Libyan National Army (LNA) for the attack.
On the other hand, Haftar's forces accused the government of bombarding the centre.
Haftar, a strongman declaring himself Libya's supreme leader, encircled Tripoli on April 4 with the apparent aim of sending a clear message to the international community that his primary objective was to sabotage the current peace plan in place, reports say.
Since then, constant fighting has been taking place in the rural areas of Tripoli. The clashes have killed nearly 600 people, injured more than 5,000 and forced more than 30,000 families to leave their homes.
The armed clashes have also severely affected thousands of migrants, mostly sub-Saharan Africans, who are in the vicinity of the capital waiting to attempt to illegally migrate to Europe or who are being held in detention centres after failing to do so.
Migrant shelters in Libya are crowded with thousands of people who have been rescued at sea or arrested by Libyan security services.
Libya has been suffering escalating violence and political instability ever since the fall of the late leader Muammar Gaddafi's regime in 2011.
( With inputs from IANS )