New Delhi, Jan. 29 -- The number of sexual abuse cases being treated at a clinic in Haiti's capital has tripled in the past four years as gang violence surges across the troubled Caribbean country, a health charity warned Wednesday.

Doctors Without Borders said it was "alarmed and outraged" by the overwhelming level of sexual and gender-based violence.

"The extent to which numbers have increased, it has shocked us," Diana Manilla Arroyo, the group's head of mission in Haiti, said in a phone interview. "It is not only the numbers, but the severity."

More than half of the patients being treated at the Pran Men'm clinic, which opened a decade ago in Port-au-Prince, were attacked by multiple members of armed groups, the charity, also known...