Amateur video provided by anti-government rebels in Sudan shows men in uniform cheering and firing weapons as they set fire to homes. Rebels say the men are government fighters and the burnings are part of a widescale effort to force civilians from the Nuba Mountains in South Kordofan province, which borders South Sudan but was not allowed to participate in the 2011 vote on secession.

Since secession, Khartoum has continued to battle a branch of the Sudan People's Liberation Movement in some of Sudan's southern provinces, where the SPLM-North hopes to win more autonomy, or perhaps a second partition.

The video is unclear, and Khartoum's ambassador to Kenya tells Al Jazeera that it is part of an SPLM-N propaganda campaign to smear Sudan's government. But if it is real, it would constitute a crime against humanity.

Peter Greste reports from Nairobi.