President Omar al-Bashir of Sudan has ordered the stoppage of oil transfers through Sudan from South Sudan from Sunday.
State radio gave no further details in a text alert that it sent to subscribers.
Oil resumed flowing in April after the two sides struck a deal in Addis Ababa, in March.
But President Bashir said in May that Sudan would stop the flow of oil if South Sudan continued to support rebels operating on Sudanese soil.
The BBC reports Sudanese army is fighting an insurgency in at least three regions.
South Sudan took nearly three-quarters of Sudan's oil production when it declared independence.
The two sides fell out over how much the South should pay to export its oil through Sudanese pipelines.
At the height of the dispute last year, the South shut down its entire oil output.
