BAMAKO, Mali -- An al-Qaida-linked Islamist militant group in control of northern Mali stoned to death a couple accused of engaging in extramarital affairs, the group's spokesman said.

The couple were publicly executed in the remote town of Aguelhok, near the vast West African nation's northern border with Algeria, on Sunday, a spokesman for the Ansar Dine group told Reuters.

"These two people were married and had extra-conjugal relations. Our men on the ground in Aguelhok applied shariah (Islamic law)," said Sanda Ould Bounama, reached by telephone on Monday.

"They both died right away and even asked for this application. We don't have to answer to anyone over the application of shariah," he said.

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A local government official told the AFP news agency that he was on the scene. "The Islamists took the unmarried couple to the center of Aguelhok. The couple was placed in two holes and the Islamists stoned them to death," he said.

"The woman fainted after the first few blows," he said. The man shouted out once and then was silent, he added.

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Most people living in northern Mali have long practiced Islam, but frustrations with the strict form of shariah being imposed by Islamists have sparked several protests in recent months.

Ansar Dine and well-armed allies, including al-Qaida splinter group MUJWA, have hijacked a separatist uprising by local Tuareg rebels and now control two-thirds of Mali's desert north, territory that includes the regions of Gao, Kidal and Timbuktu.

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Western and African governments are struggling to muster a response to the crisis as politicians in the capital Bamako continue to squabble over how the country should be governed after a March coup removed the country's president.

NBCNews.com staff contributed to this report from Reuters.

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