"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.
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.