DUBAI (REUTERS) - A Saudi court has ordered an investigation into the marriage of a 12-year-old girl in the south of the conservative kingdom, a local news website reported.

The Saudi justice ministry drafted a bill earlier this year that sets 16 years as the minimum age of marriage for girls but allows for exceptions.

A ministry spokesman could not be reached for comment but human rights activists have previously said such rules have previously been announced and not subsequently followed.

Al-Sabq website reported on Tuesday that a school principal in Samita district in the southeast of the country near the Yemeni border noticed that the fourth-grade girl had not been feeling well, and sent her to a local hospital after finding out she had been married.

The report said that a judge had asked police in the area to question the girl's husband and her father how the marriage had taken place.

No details were available on the age of the husband or the circumstances surrounding the marriage, but financial considerations have in the past prompted some Saudi families to wed young daughters to much older men in return for lavish dowries.

Saudi Arabia, a patriarchal society that applies an austere version of Sunni Islam, grants fathers guardianship over their daughters, giving them control over who they can marry and when.

Many Saudi clerics, including the kingdom's most senior religious figure Grand Mufti Sheikh Abdulaziz Al al-Sheikh, endorse the practice, subject to restrictions such as ensuring the girl has reached puberty.

Cases of child marriage, including brides as young as eight-years-old, have made headlines in local and international media in recent years, drawing heavy criticism of the conservative US ally.

In 2010, the Saudi Human Rights Commission, a government-affiliated group, hired a lawyer to help a 12-year-old divorce her 80-year-old husband.

Activists at the time saw the divorce proceedings as a test case that could pave the way for introducing a minimum age for marriage.

Saudi Arabia is a signatory of the United Nations Convention on the Rights of a Child, which considers those under the age of 18 as children.