Louise Arbour is heading to Sudan after a four-day visit to Ethiopia this week. (Associated Press)

The United Nations' top human rights official, Canadian Louise Arbour, is due to arrive in Sudan later Saturday for a tour of the troubled Darfur region.

The visit comes amid growing pressure on the Sudanese government to end fighting in the area.

The conflict erupted in 2003 when mostly non-Arab tribes revolted, accusing the Arab-led government of neglect.

Khartoum retaliated by arming mainly Arab militias, known as janjaweed, who are blamed for driving more than two million people from their homes and into squalid camps in Sudan and neighbouring Chad.

Deaths linked to the campaign number about 200,000. Jan Pronk, the UN representative in Sudan, said the fighting is killing about 400 people every month, twice the rate of a few months ago.

Arbour, the UN's high commissioner for human rights, will spend six days in Sudan, during which time she will visit conflict-wracked Darfur for the first time in two years.

Increased instability in the region means it is impossible for aid workers to reach some areas.

The UN, meantime, said it must halve the rations of millions of people in the refugee camps because of a lack of funding.