A top United Nation's envoy to Sudan has charged that little is being done to prosecute suspected criminals of war in the war-torn western Darfur region, and says worsening security is perpetuating human rights abuses. Sima Samar says that human rights abuses persist throughout Sudan, including arbitrary arrests and torture.

Amid increasing violence in Darfur, the United Nations Human Rights Rapporteur to Sudan says that there has been little accountability for war crimes in the region, and suggests that Sudanese courts set up to try war criminals have failed to do the job.

Sima Samar told reporters in Khartoum that human rights abuses persist in the region, and suggested that Sudanese special courts are unable to try war criminals.

"The security situation in Darfur is getting worse. Of course if there is lack of security there are always human rights violations," said Samar. "Since my last visit to Sudan in October there has been not much accountability for the serious crimes which have been committed in Darfur. And a special court established to bring people to justice so far has not accused or prosecuted anyone with command responsibility."

Samar called on Sudan and the international community to end the "culture of impunity," in Dafur, adding that both Sudan government forces and rebel forces are responsible for rights violations.

The special Sudanese courts were set up last spring after the international community called for Darfur war crimes suspects to be sent to the International Criminal Court in the Hague. Sudan refused to allow international intervention and instead set up its own courts to try war criminals internally.

Samar's visit comes amid calls for a transfer of peacekeeping responsibilities in the region, from African Union forces to United Nations peacekeepers. The African Union Mission is underfunded and has been called inadequate by critics who charge that the mission does not have a strong enough mandate.

Sudan has strongly resisted the call for a foreign presence in Darfur. Last week, Sudanese president Omer Al Bashir warned that Sudan would be what he called a "graveyard" for U.N. troops. Sudan has threatened to pull out of the African Union if the A.U. asks for United Nations support.

The African Union is set to meet on Friday, to discuss turning the mission over to the U.N.

The three year old Darfur conflict began when rebels rose against the Khartoum government, complaining of political and economic marginalization. Government backed Arab militias known as Janjaweed then moved to crush the rebellion. An estimated 180,000 people have died and some two million more have been displaced by the fighting.