Sudan's army on Thursday blamed South Sudanese-backed rebels for an explosion and fire in a Sudanese oil pipeline in the disputed Abyei area.
"This group received technical support from South Sudan's army to help them explode the pipeline... which led to a fire that has now been controlled," army spokesman Sawarmi Khaled Saad said in a statement.
The allegation of the South's involvement comes two days after Sudan's petroleum ministry formally told oil companies to block exports of South Sudanese crude within 60 days, reigniting tensions after weeks of calm between the two nations.
Sudan's President Omar Al-Bashir said Khartoum will not allow export revenue from South Sudanese oil "to be used in support of rebels against Sudan."
Analysts say the insurgents have humiliated authorities with recent attacks.
Saad said Justice and Equality Movement (JEM) insurgents from Darfur "came from inside South Sudan" to carry out the pipeline attack at 9:00 pm (1800 GMT) on Wednesday.
A JEM spokesman told AFP he had no information about such an incident.
An oil ministry source said only that there was "a defect" in the pipeline and that experts were on their way to the area.
An Abyei resident familiar with the incident said it occurred several kilometres from Difra after people released oil from the line and then set it alight.
"It became a huge fire and they couldn't control it," said the resident.
Juba denies supporting insurgents in the north and, in turn, has accused Khartoum of backing rebels on southern territory.
"We deny that we have any link with the South Sudanese army," JEM spokesman Gibril Adam Bilal told AFP.
A UN panel of experts reported in February that it had "clear and compelling evidence" that last year JEM used a former chicken farm in South Sudan as a base for about 800 fighters.
On Sunday, Khartoum froze nine security and economic pacts with the South, including a deal to restore economically vital oil shipments through its Red Sea export terminal.
Despite these moves, Khartoum said it remained committed to good relations if the South's government ended its rebel support.
South Sudan became independent two years ago under a peace deal that ended a 22-year civil war. It separated with most of Sudan's 470,000 barrels per day of oil production but the export infrastructure remains under northern control.
Until March, when the two countries reached detailed timetables to implement the nine agreements, the two sides had not been able to agree on how much Juba should pay to use the pipeline.
The deals had been held up for months because of Sudan's concerns that the South was backing rebels.
Those concerns have now resurfaced publicly even though the two sides had begun jointly monitoring a demilitarised border buffer zone along with United Nations peacekeepers.
The damaged pipe carries domestic Sudanese crude and is not part of the main export line.
Abyei's status is disputed by both Sudan and South Sudan. It currently has no administration but is controlled by the UN peacekeeping force.