The western region has been mired in conflict since 2003, when ethnic insurgents rebelled against President Omar al-Bashir's Arab-dominated regime, complaining of marginalisation.
"The net displacement figure for Darfur since January 2015 is up to 166,000, nearly 100,000 confirmed and some 66,000 reported to have been displaced," said Ivo Freijsen, head of the UN's Khartoum Office for the Coordination of Humanitarian Affairs.
Freijsen said the UN had been unable to fully verify the figure of 66,000, but was trying to check the number.
But Freijsen warned that the humanitarian situation in the region is still "a very mixed picture".
He said the UN is still concerned about the 2.5 million internally displaced people in the region who have fled their homes since the outbreak of the conflict, and is working with Khartoum to find long-term solutions for them.
West Darfur is also facing an outbreak of dengue fever, with 244 reported cases and 110 fatalities since late August, Freijsen said.
Sudan's Bashir is wanted by the International Criminal Court on war crimes charges over his alleged role in the brutal counter-insurgency unleashed to crush the rebels.
In September, Bashir announced a two-month ceasefire in a bid to encourage the rebels to join national dialogue talks.
The talks began last month and are aimed at resolving the conflict in Darfur as well as those in Blue Nile and South Kordofan states, where the Sudan People Liberation Movement-North is also battling Bashir.
In turn, Darfur-based rebels who are part of the Sudan Revolutionary Front alliance announced a six-month halt in fighting in October.
The UN says some 300,000 people have been killed in Darfur since 2003, while Khartoum puts the toll at 10,000.
