Islamists occupying the northern Mali town of Aguelhok stoned an unmarried couple to death in front of about 200 people on Sunday, two local government officials said.

"I was there. The Islamists took the unmarried couple to the centre of Aguelhok. The couple was placed in two holes and the Islamists stoned them to death," said a local government official on condition of anonymity.

"The woman fainted after the first few blows," he said, adding that the man had shouted out once and then fallen silent.

A second official confirmed the information, saying the couple had two children, the youngest of which was six months old.

"They were living in the bush, they were brought to town by the Islamists who stoned them to death. People came out to watch, there were witnesses," he said, also not wishing to be identified.

The small town in the region of Kidal near the Algerian border was one of the first to be captured by Tuareg separatists rebels on January 24.

Some 82 civilians and soldiers were summarily executed, France said earlier this year, accusing the rebels of using al Qaeda style tactics.

The Tuareg rebellion sparked a coup d'etat in March by angry and overwhelmed soldiers, but the chaos only allowed the desert nomads and Islamists fighting on their flanks to seize the country's north, an area larger than France.

The Islamist groups, which experts say are acting under the aegis of al Qaeda in the Islamic Maghreb (AQIM) have since chased out the Tuareg separatists and are firmly in control of the region.

AQIM allies Ansar Dine (Defenders of Faith) are holding Aguelhok.

In Timbuktu they have also implemented strict Islamic law, and have destroyed ancient World Heritage sites which they consider idolatrous.