AMMAN, Jordan (CNN) -- A 12-year-old Yemeni girl, who was forced into marriage, died during a painful childbirth that also killed her baby, a children's rights group said Monday.

Fawziya Ammodi struggled for three days in labor, before dying of severe bleeding at a hospital on Friday, said the Seyaj Organization for the Protection of Children.

"Although the cause of her death was lack of medical care, the real case was the lack of education in Yemen and the fact that child marriages keep happening," said Seyaj President Ahmed al-Qureshi.

Born into an impoverished family in Hodeidah, Fawziya was forced to drop out of school and married off to a 24-year-old man last year, al-Qureshi said.

Child brides are commonplace in Yemen, especially in the Red Sea Coast where tribal customs hold sway. Hodeidah is the fourth largest city in Yemen and an important port.

More than half of all young Yemeni girls are married off before the age of 18 -- many times to older men, some with more than one wife, a study by Sanaa University found.

While it was not immediately known why Fawziya's parents married her off, the reasons vary. Sometimes, financially-strapped parents offer up their daughters for hefty dowries.

Marriage means the girls are no longer a financial or moral burden to their parents. And often, parents will extract a promise from the husband to wait until the girl is older to consummate the marriage.

Children's organization UNICEF issued a statement Monday saying: "Child marriages violate the rights of children in the most deplorable way. The younger the girl is when she becomes pregnant, the greater the health risks for her and her baby.

"Girls who give birth before the age of 15 are five times more likely to die in childbirth than women in their 20s. Child marriage denies girls of their childhood, deprives them of an education and robs them of their innocence."

"More must be done to address the underlying causes in order to prevent tragic deaths like those of 12-year-old Fawziya and her baby," the statement added.

The issue of Yemeni child brides came to the forefront in 2008 with 10-year-old Nujood Ali.

She was pulled out of school and married to a man who beat and raped her within weeks of the ceremony.

To escape, Nujood hailed a taxi -- the first time in her life -- to get across town to the central courthouse where she sat on a bench and demanded to see a judge.

After a well-publicized trial, she was granted a divorce.

The Yemeni parliament tried in February to pass a law, setting the minimum marriage age at 17. But the measure has not reached the president because many parliamentarians argued it violates sharia, or Islamic law, which does not stipulate a minimum age.