After a day of fierce fighting, troops from South Sudan captured an oil-rich border town that is claimed by Sudan, whose troops withdrew under the onslaught, a Sudanese government minister said Wednesday.

The military advance by South Sudan into territory it claims but which is internationally recognized as Sudan's brought swift condemnation from the United States and Britain. Both nations, along with the U.N. Security Council, urged South Sudan to withdraw from the town of Heglig and condemned the bombings of South Sudan territory by Sudan.

Sudan's ambassador to the United Nations, Daffa-Alla Elhag Ali Osman, said he had filed a complaint to the Security Council condemning the "heinous attack" on Heglig and demanding South Sudan's withdrawal.

"We will decide to retaliate, and retaliate severely, deep inside South Sudan" if the Security Council doesn't address the situation, Ali Osman told reporters. He added, "We know they are a very fragile state, they have a lot of problems inside. We do not want to escalate this war, which they started, because it is not going serve the interest of either country."

U.N. Secretary-General Ban Ki-moon said he was "alarmed by the escalation in fighting" and said both countries should withdraw their forces from each others' territory.

"We condemn South Sudan's military involvement in the attack on and seizure of Heglig, an act which goes beyond self-defense and has increased tensions between Sudan and South Sudan to dangerous levels," U.S. State Department spokeswoman Victoria Nuland said.

Heglig lies along the ill-defined border between the two African nations and has been the focal point of nearly two weeks of clashes between their armies. The region is home to oil facilities that account for around half of Sudan's oil production, a critical source of income for the country's flagging economy.

The two rivals fought a civil war that lasted decades, and any increase in their sporadic border clashes raises the risk of a return to all-out war. The two sides never reached a deal to share the region's oil resources or delineate their exact border.

Sounding the alarm, a South Sudan official said the fighting is "spreading all over."

The Sudanese government admitted late Wednesday that South Sudan's army, known as the SPLA, has taken over Heglig and that its forces have withdrawn to regroup. The town is 100 kilometers (60 miles) east of the disputed region of Abyei, whose fate was left unresolved when South Sudan split last year from Sudan.

Sudan Information Minister Abdulla Ali Masar said the SPLA, which he said was supported by "foreign forces" as well as the Sudanese Revolutionary Front (SRF) of the Darfur rebel movement and SPLA-North, waged a three-pronged attack on the area around Heglig. He did not identify the foreign forces.

"Those huge, well-equipped forces managed to enter the town ... and looted belongings of the civilians and companies," Masar told reporters in Khartoum, the capital of Sudan.

"The Sudan Armed Forces stood up courageously to this hostile subversive act, but in view of these tremendous forces with which South Sudan attacked the Heglig area, SAF, in a tactical move, was forced to retreat to Kharasanah," he said.

Masar said Sudan's forces would reorganize their ranks and prepare to "drive back the aggressors" and recapture Heglig.

Ali Osman, Sudan's U.N. ambassador, said South Sudanese military forces had advanced 30 kilometers (18 miles) north of Heglig.

A 2009 ruling by the Permanent Court of Arbitration in the Hague placed Heglig in South Kordofan, Sudan. But South Sudan has disputed the ruling, asserting that the region is in South Sudan's Unity State.

South Sudan's army said it moved into Heglig on Tuesday after repelling an attack launched by Sudanese Armed Forces against an SPLA position near the border town of Teshwin.

SPLA spokesman Col. Philip Aguer said several Sudanese MiG-29 fighter jets bombed the area on Monday and Tuesday. Aguer said several SPLA soldiers were wounded in the attack.

Aguer said South Sudan's forces are pushing through the area to prevent further attacks from forces there.

"Our main goal is to secure the territories of South Sudan and protect its people," said Aguer. "Sudan and its allies, militiamen that have been trained in Heglig and Karsana, have been attacking us from there for last two years."

South Sudan's move into Heglig follows separate alleged attacks in South Sudan's Unity state, near Abiemnom.

Aguer said a series of bombing attacks by Sudan on Tuesday wounded four civilians. Benjamin said the target was a "strategic bridge" linking Unity with neighboring Warrap state. Abiemnom has not been a recent site of conflict between the two countries.

"The war is widened," said South Sudan Information Minister Barnaba Marial Benjamin. "The battle is raging. It is spreading all over."

The U.S. State Department's Nuland said it is critical that leaders in both countries immediately exercise maximum restraint.

Britain's Minister for Africa, Henry Bellingham, said the "cycle of provocative and irresponsible acts" by both militaries must end immediately. He called South Sudan's move into Heglig "completely unacceptable."

"I call on both sides to establish a cease-fire and withdraw all forces immediately from one another's territory," he said.

The continued clashes have dimmed hopes for a resolution between the two countries on a host of issues left over from their July split, including oil-sharing, citizenship issues and the demarcation of the border.

Sudan President Omar al-Bashir was scheduled to visit South Sudan for a summit April 3, but the talks were scrapped in the wake of the clashes.

President Barack Obama earlier this month called South Sudan President Salva Kiir to ensure that South Sudan's military exercises maximum restraint and is not involved in or supporting fighting along the border.

In New York on Wednesday, the U.N. Security Council discussed its peacekeeping mission in Abyei, to the west of the current conflict.


Saeed reported from Khartoum. Associated Press Writer Peter James Spielmann contributed to this story from the United Nations.