Satellite images show a key part of the oil infrastructure in Sudan's contested Heglig region was destroyed during recent border fighting with South Sudan, a monitoring group said on Sunday.
South Sudan seized Heglig, a border region which accounts for about half Sudan's 115,000 barrel-a-day oil output, on 10 April, saying it was acting in self defence after Sudan launched a ground attack from the area.
On Friday South Sudan, under international pressure to withdraw, said it was pulling out to create an environment for talks, and the Sudanese army later said it had "liberated" the area. South Sudan said its troops were bombed as they withdrew.
The Satellite Sentinel Project, founded by Sudan activists including Hollywood actor George Clooney, said recent satellite imagery showed "an oil collection manifold" in the Heglig area had apparently been blown up.
"The destroyed structure appears consistent with a collection manifold because of its shape and its location at the junction of multiple pipelines," it said in a statement, adding that a collection manifold connects piping systems together to divide or combine different flows of oil.
"The destruction of this particular collection manifold would likely result in the immediate cessation of oil flow in the area," it said.
The group said the images were captured on April 15, but it could not tell whether the damage was caused by aerial bombardment or ground action. It was not clear when the oil equipment had been damaged or by which side.
Access to the remote border area is limited, making it hard to verify often contradictory statements from the two countries.
Landlocked South Sudan, which seceded from Sudan after decades of civil war and became independent in July, produces 350,000 barrels a day of crude, but shut down production in January in a row with Khartoum over payments for exporting its oil through Sudan.
Oil is the mainstay of both countries' economies, providing South Sudan with about 98 percent of its state revenue.
Since southern independence, the two sides have embarked on an increasingly bitter dispute over the demarcation of the border, southern oil export payments and the division of the national debt.