Guterres will be on a 10-day visit to Sudan, Chad and Kenya, a spokesperson said.

Following meetings with Sudanese President Umar al-Bashir and other government officials, Guterres will on Wednesday visit Darfur, where fighting has displaced 1.9 million civilians.

"In Darfur, he will be underlining the need for the government of Sudan to provide additional security to its own citizens," Kitty McKinsey, regional spokesperson for UNHCR, told IRIN on Monday.

"Security needs to be provided for the displaced people in the camps as well as in the villages where they would like to return to," she added. "It is the responsibility of the Sudanese government."

McKinsey said the visit was also intended to lay emphasis on the importance of the stalled Darfur peace talks in the Nigerian capital, Abuja.

"More broadly, he is trying to refocus some of the international attention on the continuing needs of the people of Darfur," she said.

"Last year, Darfur was called the worst humanitarian crisis in the world, but this year the region has disappeared from the international radar screen, while people continue to suffer," McKinsey stressed. "Things have not gotten any better."

The war in Darfur began in February 2003 and pits Sudanese government troops and militias allegedly allied to the government, against rebels fighting to end what they describe as the marginalisation of and discrimination against the region's inhabitants by the state.

Following his visit to Darfur, Guterres is scheduled to visit Iridimi and Iriba in eastern Chad, where 200,000 people who fled the fighting in Darfur have found shelter in 12 camps.

"He wants to find out for himself, from the displaced, what their concerns are," McKinsey said.

The UNHCR chief is due to meet Chadian President Idriss Deby on Friday, and thereafter visit southern Sudan where he will inspect preparations for the return of refugees, including the rebuilding of schools and hospitals and the demining of roads.

McKinsey noted that UNHCR was anticipating a substantial influx of returning refugees following the signing of a peace agreement for the separate north-south conflict in January.

UNHCR estimates that more than four million people remain displaced by conflict in southern Sudan.