A satellite monitoring group says Sudan is trying to block civilians in the country's violence-plagued Southern Kordofan state from fleeing to safety.

New images released Friday by the U.S.-based Satellite Sentinel Project, and analyzed by the Harvard Humanitarian Initiative, show plumes of smoke rising from an area known as Toroge .

The initiative's Nathaniel Raymond tells VOA the pictures are some of the most striking captured by the project to date. He says they show a clear attempt by Sudan's armed forces to create a choke point for civilians fleeing to a refugee camp in South Sudan, about 45 kilometers to the south.

The centers says it has reports that fighting in the area has been raging for several days between Sudanese Armed Forces and the rebel Sudan People's Liberation Army-North .

The rebels are believed to support the south, which split from the north in July.

Earlier this week, the satellite monitor said other images show the Sudanese military preparing to launch an offensive against the Nuba people in Southern Kordofan's Kauda Valley.

Khartoum has claimed that many Nuba people back South Sudan.

The watchdog group said about 200,000 Nubas fled to Kauda Valley to flee air attacks in other parts of the state.

In recent months Sudan has carried air and ground attacks in Southern Kordofan, displacing tens of thousands of people and forcing many to flee into neighboring South Sudan.

The United Nations has expressed concern about the situation in the state. Khartoum has denied a U.N. request to allow aid workers to enter the area to provide humanitarian assistance.

The Harvard Humanitarian Initiative's Raymond also rejected accusations by Sudan that the project's efforts are aiding the rebels.

Raymond said the initiative's only consideration is the safety of civilians, and that previous images have documented “clear evidence of mass atrocities against the civilian populations there.”