Halima Ibrahim Abdurrahman, 20, was killed in front of hundreds of people, mostly women and children, in the town of Wajid, 250 miles (400km) north-west of the capital, Mogadishu.

Sheikh Ibrahim Sheikh Abdirahman, a judge for an Islamic militant group of Al-shabaab in the Wajid district, the Bakool province said that Abdurrahman engaged in illegal sex with an unmarried man Nanah Mohamed Madey.

Madey, 29, was given 100 lashes for his conduct. "They have admitted to the acts in the court,” the judge said.

The Somali Islamist group of Al-shabaab controls much of southern Somalia, while the western backed government runs only a little of the capital city Mogadishu.

The incident is the fourth time that Islamists have stoned a person to death for adultery during the past year. The group has stoned to death two men in the same town after accusing them of spying. A 13-year-old girl was stoned to death for adultery in the port town of Kismayo some 300 km south of Mogadishu last year.

Somalia has not had an effective government since warlords overthrew dictator Mohamed Siad Barre in 1991.