The WHO said in a tweet that 614 others had been wounded since commander Khalifa Haftar launched an offensive earlier this month to take Tripoli, which is currently controlled by a UN-backed government.
In another, earlier tweet, it denounced "repeated attacks on health care workers, vehicles" during the fighting, which began on April 5.
Earlier this week, the UN said the fighting had displaced more than 8,000 people.
Egyptian President Abdel-Fattah el-Sissi met with Haftar in Cairo to discuss the offensive amid mounting international pressure to end the campaign. Egypt and France maintain friendly relations with Haftar.
Read more: Could Libya be Russia's new Syria?
Lawless nationThe current violence pits Haftar's self-styled Libyan National Army, which backs a rival government in the east of the country, against an array of militias that support the Tripoli administration.
Observers fear a civil conflict matching the 2011 rebellion that led to the ouster and death of dictator Moammar Gadhafi.
Since Gadhafi's ouster, the country has been in a state of partial lawlessness, with militias of various political persuasions vying for control.
Read more: Khalifa Haftar: Libya's military strongman
ls,tj,ng/se (AFP, AP)
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