Mali's interim government has condemned the stoning death of two people by Islamist militants who control the country's north.

In a statement Tuesday, the government said it learned of the killings with “indignation and astonishment” and denounced what it called the dark-age practice of stoning. It promised that the killings “will not go unpunished.”

The militant group Ansar Dine said it executed a man and a woman in the small town of Aguelhok on Sunday.

A group spokesman told VOA that the unmarried couple committed adultery, and received “the punishment called for under Islam: death.”

Reports from the area said Islamist fighters placed the man and woman into holes and threw rocks at their heads until they died. At least 200 people watched the killings in the center of town.

The government Tuesday repeated its vow to do all it can to retake the north.

Islamist groups and Tuareg separatists seized control of northern Mali in April, after renegade soldiers overthrew the government in Mali's capital, Bamako.

The al-Qaida-linked Islamists have since taken full control of the north and imposed a strict version of Islamic law, despite protests from much of the population.

On Sunday, Mali's interim President Dioncounda Traore announced plans to overhaul his transitional government and request foreign help in retaking northern regions.