A Nigerian woman sentenced by an Islamic court to death by stoning for having a child outside wedlock began her appeal process Monday, as European politicians denounced the sentence.

Safiya Hussaini Tungar-Tudu, 35, was convicted of adultery last October in the northern state of Sokoto and sentenced to be stoned while buried up to her waist in sand.

Opposition to Islamic law, or shariah, in predominantly Muslim northern Nigeria has left thousands of dead in religious clashes since early 2000, authorities say.

European parliament members sent a letter to President Olusegun Obasanjo thanking him for intervening to prevent Hussaini's execution over the weekend, and urging that capital punishment be abolished in Nigeria.

During a brief court appearance at the start of Hussaini's appeal in Sokoto city, 10 defense lawyers argued the Islamic court had failed to determine whether she had ever been "legally married," a prerequisite for adultery.

If she wasn't married, the defense said, the court should have treated her case as premarital sex, which carries a lesser punishment under Islamic law.

The lawyers also argued that female residents of Sokoto state were allowed to conceive a child with their former husbands up to seven years after they had been divorced.

During the October trial, Hussaini said she had been divorced for about two years. The baby girl prosecutors say was conceived outside wedlock is now about 1 year old.

Defense lawyers also said Hussaini's child had been conceived before shariah law was officially imposed in Sokoto state in January 2001, and that the death penalty prescribed by Islamic doctrine could not be carried out retroactively.

"The (shariah court's) legal procedure was irrevocably bad, therefore the judgment should be declared null and void," said Abdulkadir Imam Ibrahim, the lawyer leading her defense.

Prosecutors asked for time to study defense arguments, and the case was postponed until March 18. If Hussaini loses her appeal, she can take her case to Nigeria's Supreme Court.

In a letter made public Monday, 77 members of the European Parliament asked Obasanjo to block the death penalty. His government has financially backed Hussaini's legal defense.

Writing on behalf of the Europeans, lawmaker John Corrie thanked Obasanjo for intervening to prevented the stoning from taking place Saturday and urged him to set aside the execution.

"No one should underestimate the strong views in many countries around the world that all laws should respect international human rights standards," Corrie wrote. "I trust that you as the president of Nigeria will do all in your powers to stop this and future executions."

On Jan. 3, a 35-year-old man convicted of murdering a woman and her two toddlers was hanged in Katsina state, the first execution since Islamic law began being implemented by a dozen predominantly Muslim states in Nigeria in early 2000.

Nigeria, a nation of 120 million, is riven by religious, ethnic and political divisions that periodically flare into violence. Obasanjo won the presidency in 1999, ending 15 years of military rule.