Thousands of girls under 14 are reported to have been married off to richer, much older men in Saudi Arabia.
Many Saudis have expressed their disgust at the marriage on the Internet, saying it amounts to child abuse.
Human rights activists have also urged Saudi authorities to intervene "as soon as possible to save this child from tragedy."
According to local sources, the girl escaped the arranged marriage after locking herself in a room on their wedding night for two days. She eventually fled back to her parents' house.
The 90-year-old man insists the marriage was "legal and correct" and has vowed to file a lawsuit against the girl's parents if she did not return.
But many believe the marriage was religiously invalid since in Islam it must be based on mutual consent.
Despite strong public demand for the establishment of a minimal age for marriage, conservative religious scholars refuse to accept a state-driven legal ban on child marriage.
Marriage is viewed in many Arab countries, including Saudi Arabia, as a daughter's destiny. Relatives arrange marriages primarily to get rid of a mouth to feed and girls who refuse to agree to a forced marriage are often seen by their families as rebellious and shameful.
Reports say ten million girls under the age of 18 are married every year with 1.5 million of them being under the age of 15.