"The toll from the armed conflict in Tripoli, Libya continues to climb. As of 19 May, 510 people have died and 2,467 people have been wounded," WHO tweeted, Xinhua news agency reported.
The east-based army, led by Khalifa Haftar, has been leading a military campaign since early April to take over Tripoli, where the UN-backed government is based.
Libya has been struggling to undergo a transitional period amid chaos since the fall of former leader Muammar Gaddafi in 2011.