KHARTOUM, Sudan -- A Muslim-by-birth Sudanese woman who married a Christian man was sentenced to death Thursday after she refused to recant her Christian faith, judicial officials and an Amnesty International researcher said.

Meriam Ibrahim, whose father was Muslim but her mother Christian, was convicted of "apostasy" on Sunday and given four days to repent and escape death, officials said. The 26 year old was sentenced after that grace period expired, the officials said, speaking on condition of anonymity in line with regulations.

As in many Muslim nations, Muslim women in Sudan are prohibited from marrying non-Muslims, though Muslim men can marry outside their faith. By law, children must follow their father's religion.

The court in the capital, Khartoum, also ordered that Ibrahim be given 100 lashes for committing "zena" -- an Arabic word for illegitimate sex -- for having sexual relations with her husband, a Christian from southern Sudan.

Ibrahim's case first came to the attention of authorities in August last year, when members of her family complained that she was born a Muslim but married a Christian man. Authorities charged her with "zena" and she was put on trial. She was first detained in a Khartoum jail in February and charged with apostasy after she declared in court that she was raised as a Christian by her mother, said Manar Idriss, Amnesty International's Sudan researcher.

Ibrahim is eight months pregnant and has with her in jail her 18-month-old son, Idriss said.

There have been a number of cases over the years of Sudanese convicted of apostasy, but they all escaped the gallows by recanting their faith. Ibrahim is the first to be sentenced to death for apostasy, Idriss said. Ibrahim's lawyers plan to appeal the sentence.

Thursday's sentencing drew condemnation from Western embassies in Khartoum and international rights groups, including the London-based Amnesty International.

"The fact that a woman has been sentenced to death for her religious choice, and to flogging for being married to a man of an allegedly different religion, is appalling and abhorrent," Amnesty said in a statement. "Adultery and apostasy are acts which should not be considered crimes at all."

The group also called for Ibrahim's immediate and unconditional release.

Sudan introduced Islamic Shariah laws in the early 1980s, a move that contributed to the resumption of an insurgency in the mostly animist and Christian south of Sudan. An earlier round of civil war lasted 17 years and ended in 1972. The south seceded in 2011 to become the world's newest nation, South Sudan.

Sudan's current ruler, Omar Bashir, is an Islamist who seized power in a 1989 coup.