"New imagery from the Satellite Sentinel Project, or SSP, confirms that the Sudan Armed Forces (northern army -- SAF) control the town of Kadugli in Sudan's tense border region of South Kordofan, and that thousands of civilians have been displaced, , monitors said.

"The images support reports from the ground that SAF soldiers remain locked in a tense conflict with elements of the Sudan People’s Liberation Army (of the south -- SPLA) in South Kordofan.

"The images reveal that SAF's deployment of forces is consistent with UN documents indicating that a major SAF offensive could occur soon."

The US monitoring group, which was set up by Hollywood star and rights activist George Clooney last year, said the satellites images that were taken on June 17 were the first to show thousands of people seeking shelter around the main UN compound near Kadugli.

Heavy fighting has raged across South Kordofan since June 5 between the SAF and northern troops aligned to the army of the south that Khartoum has vowed to crush using all available means, including air strikes and heavy artillery.

World leaders including US President Barack Obama and UN chief Ban Ki-moon have called for an immediate ceasefire.

Sudanese church leaders and activists say the army's campaign forms part of a government policy of "ethnic cleansing", targeting South Kordofan's indigenous Nuba peoples who fought with the SPLA during the 1983-2005 civil war.

Khartoum strongly rejects those claims, insisting it is protecting civilians.

Eyewitnesses have described scenes of terror and carnage in Kadugli, with pro-government forces executing suspected sympathisers of the southern-aligned troops during house-to-house searches, and dead bodies lying in the streets.

The conflict has so far caused more than 60,000 people to flee their homes, according to UN estimates, including 30,000 children, amid ongoing fighting that the UN humanitarian office says has "seriously compromised" the delivery of emergency aid.