The Emergency Lawyers group said the Rapid Support Forces (RSF), battling the army for more than two years in the country's devastating civil war, "arrested dozens of young people and executed more than 27, accusing them of collaborating with the army".

The toll could not be independently checked by AFP.

Emergency Lawyers said in a statement that the killings took place in En Nahud, a transit point in West Kordofan state used by the army to send troops to Darfur in western Sudan.

The group said the RSF had released prisoners from the town's prison, "provoking a situation of chaos and the collapse of public order".

The RSF said Friday that its forces had also taken El-Khoei, a town about 100 kilometres (60 miles) east of En Nahud. Witnesses said army forces had withdrawn toward the North Kordofan state capital of El Obeid.

The war between the army, led by Abdel Fattah al-Burhan, and the RSF of his former deputy Mohamed Hamdan Daglo, has left tens of thousands of people dead and displaced 13 million.