Sudan's government says it will not allow international investigators into the troubled province of Darfur to collect evidence on alleged war crimes.
No high-level officials have been prosecuted for the atrocities in Darfur
The ban comes as the chief prosecutor from the International Criminal Court told the UN Security Council that he wanted more co-operation from Sudan.
Luis Moreno Ocampo said he had identified mass killings and rape but had not decided who to prosecute.
Some two million people have fled their homes in the three-year Darfur war.
Sudan's Justice Minister Muhammad Ali al-Mardi told the BBC that the ICC had no jurisdiction to try Sudanese nationals.
"We have the national law authority... The government is willing and able to try to these cases," he said.
The BBC's Jonah Fisher in Khartoum says only a few low-level military officers have faced charges over the violence in Darfur, which has left tens of thousands dead.
Millions of people have been displaced by the conflict
An earlier investigation by a UN-appointed commission drew up a list of 51 possible suspects for alleged war crimes in Darfur.
But Mr Ocampo said the ICC would conduct its own investigations and no decision had been taken as to whom to prosecute.
On Monday, lobby group Human Rights Watch called for senior Sudanese officials - including the president - to be investigated for crimes against humanity in Darfur.
Its latest report names more than a dozen civilian and military officials it says helped co-ordinate militias and armed forces who attacked civilians.
It adds that the leadership in Khartoum relied on the civilian administration, the military and Janjaweed militias to implement a counter-insurgency policy that deliberately targeted civilians.
A Sudanese official dismissed the report as "ridiculous" and "baseless".
Sudan's government has said that the violence in Darfur is a tribal conflict and the attacks are carried out by militias and rebels.
It denies that the state has co-ordinated the violence.