Of all finalized marriages in Yemen, nearly 65 percent of females were underage, rising to 70 percent in rural areas, Gulf News reported.
Among the males, 7 percent were under age 18.
Yousuf Abu Ras, head of the Yemeni Organization for Economic and Social Development, said the country's laws and people's perceptions need to be changed to curb underage marriages.
"The issue is related to the country's culture," he said. "Any legal amendment will come from above, and it doesn't reach the roots of the society. The issue needs more awareness and enlightenment efforts, [to succeed]."
A Sanaa court allowed two girls -- ages 8 and 9 -- to annul their marriages last year, and a civil society group intervened in the marriage of a man his his 30s to a second-grader.