South Sudan's army on Friday rejected any involvement in an explosion in a Sudanese oil pipeline in the disputed Abyei area, after being accused by Khartoum of backing rebels.
"It is an outright fabricated lie," South Sudan deputy army spokesman Malaak Ayuen told AFP, adding that the only news he had of Wednesday's blast was from media reports.
Ayuen had no direct information of the attack, he said, because his men were south of Abyei, which lies on the border between the nations.
Sudan's army has blamed the explosion in the Difra region on rebels it said were given technical support by South Sudan's army.
"We do not support any rebel forces and we do not have any of our troops in those regions..., because we have pulled our forces back in line with the agreements that were signed," Ayuen said.
"Sudan knows this, they know their accusations are hollow."
The allegation of the South's involvement came 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 former civil war foes.
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 that insurgents have humiliated authorities with recent attacks.
Sudan army spokesman Sawarmi Khaled Saad said Justice and Equality Movement (JEM) rebels from Darfur "came from inside South Sudan" to carry out the pipeline attack.
"JEM didn't blow up this pipeline," the rebels' spokesman Gibril Adam Bilal said in a statement Thursday. He claimed government officials cooked up a scenario "to blow up the pipeline between Difra and Heglig and then accuse JEM."
An oil ministry source said only that there was "a defect" in the pipeline and that experts were on their way to the area.
The blaze occurred several kilometres (miles) from Difra after people released oil from the pipeline and then set it alight, said an Abyei resident familiar with the incident.
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 support for rebels.
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.