A spokesman for Islamist group the Movement for Oneness and Jihad in West Africa confirmed to The New York Times that a man's hand was amputated in northern Mali after he was accused of robbery.
"He stole. God has told us to cut off the hands of thieves," said spokesman Aliou Mahamar Toure. "It's in the Koran."
Islamic rebels, including some aligned with al-Qaida, have razed protected heritage sites in Timbuktu, saying they weren't in line with their interpretations of Shariah law. A couple was stoned to death in public last week by Islamic groups in the north for allegedly having a child out of wedlock.
The International Criminal Court announced in July it started a preliminary investigation into possible crimes committed in Mali since the beginning of the year.
The interim administration in Bamako said atrocities committed in the north were "cloaked in a false veil of religion" and "reinforce the inevitability of military action," the Times reports.
Members of the Economic Community of West African States have called on the United Nations to pass a resolution that would permit the use of force to settle issues in Mali, simmering since an April coup.