A Nigerian woman sentenced to death by stoning for adultery has arrived at a northern Nigeria courthouse to launch her appeal.

An Islamic court is expected to begin hearing Amina Lawal's appeal Wednesday. Dozens of riot police have surrounded the courthouse in Katsina, but there have been no reports of problems.

Ms. Lawal was convicted in 2002 for giving birth out of wedlock. A northern Sharia court, which is governed by strict Islamic law, handed down the death by stoning sentence.

The court delayed her appeal twice because not enough judges were available to hear her case.

Human rights groups worldwide have called for Lawal's sentence to be lifted. Nigerian President Olusegun Obasanjo has said he will not allow it to be carried out, but warned he would not intervene directly.

Twelve Muslim states in northern Nigeria have established Sharia law in recent years. So far, no death by stoning punishments have been carried out.