UN Secretary General Ban Ki-moon on Monday urged Sudan to allow peacekeepers to investigate allegations of a mass rape in Darfur after Khartoum blocked the probe for a second time.
The UN-African mission (UNAMID) team was barred entry to the village of Tabit on November 4 following a report that Khartoum troops had raped 200 women and girls there but returned five days later and found no evidence.
The mission vowed to follow up the investigation but was again denied access to Tabit on Sunday by the Sudanese foreign ministry.
"Only a full investigation by UNAMID will help shed light over these serious allegations," Ban said in a statement.
He urged Sudan "to grant UNAMID unfettered access, without further delay, to Tabit and its population so that these reports can be verified."
A local news website had reported Sudanese troops entered the village of Tabit on October 31 after a soldier went missing and raped 200 girls and women. Khartoum has denied the allegations.
While UNAMID said it found no evidence after its first visit to Tabit, an internal UN report obtained by AFP said the Sudanese military had tried to intimidate villagers as the peacekeepers interviewed them.
During the team visit, there was a heavy presence of Sudanese soldiers who followed the monitors and recorded interviews with the villagers, according to the report.
Sudanese foreign ministry spokesman Yousif al-Kordofani said Sunday "the government of Sudan decided not to allow the mission to visit the village another time."
"The accusations of mass rape have been met with the strong resentment of the people of the village of Tabit and the surrounding villages and provoked their anger, raising tensions in the area," Kordofani said in a statement, suggesting it was too dangerous for UNAMID peacekeepers to visit.
He added UNAMID had also sought permission from the regional authorities in Darfur to visit the area on November 15 while discussions were ongoing with the foreign ministry about a request to visit on November 17.
UNAMID deployed to Darfur in 2007 to protect civilians and secure humanitarian aid. Last month an investigation by the United Nations criticized the mission for under-reporting crimes in the region.
Sudanese President Omar al-Bashir, 70, is wanted by the International Criminal Court for alleged war crimes in Darfur.
More than 300,000 people have been killed in some 11 years of conflict in the region, with another two million displaced, according to the UN.