South Sudan's army vowed Tuesday to hold their positions in a contested oil field seized from Khartoum's army, one week after the outbreak of bitter fighting that has raised fears of a wider war.

Despite air strikes and a reported counter-attack by Khartoum's Sudan Armed Forces (SAF) to retake the disputed Heglig oil field, the South's Sudan People’s Liberation Army (SPLA) said it would not withdraw from the battle zone.

Questions are being raised in Sudan over how easily South Sudanese forces marched in and seized Khartoum's main oilfield, worsening an economy already mired in crisis.

Analysts say the South's invasion of the Heglig area last Tuesday has put Defense Minister Abdelrahim Mohammed Hussein under scrutiny.

Sudan parliament voted unanimously on Monday to brand the government of South Sudan an enemy, after southern troops invaded the north's main oilfield.

"The government of South Sudan is an enemy and all Sudanese state agencies have to treat her accordingly," the parliament's resolution said.

Progressive Socialist Party leader MP Walid Jumblat hoped on Monday that the government would tackle the people’s concerns without preconditions.

He urged in his weekly editorial in the PSP-affiliated al-Anabaa magazine political powers to exercise “some humility” in tackling pending issues at cabinet.

Sudanese warplanes bombed a U.N. peacekeepers' camp damaging the base but causing no casualties, the first such attack since a recent spike in violence between the rival states, officials said Monday.

Bombing raids on Sunday also killed nine civilians elsewhere in South Sudan's Unity border state, the area's information minister Gideon Gatpan said.

The first batch of Sudanese prisoners of war captured in days of bloody fighting arrived in the South Sudanese capital Sunday, as the South's army said clashes continued in contested border regions.

"We are respecting the international laws on war," South Sudanese army spokesman Philip Aguer told reporters, adding the prisoners were captured in the contested Heglig oil field, seized last week by Southern troops.

Five people were killed and six wounded in Sudanese airstrikes on Bentiu, capital of the oil-rich South Sudan border state of Unity, on Saturday.

"Three bombs were released next to Bentiu Bridge, and at the moment one person is confirmed killed. But they did not break the bridge," said Gideon Gatfan, spokesman of the Unity State government.

The South Sudan army claimed Saturday to still be in control of Heglig after Khartoum said it had launched an offensive to recapture the disputed oil hub.

"The SPLA is controlling Heglig," spokesman Philip Aguer told AFP. He said that the Southern army had repelled soldiers of the Sudanese Armed Forces in the village of Kelet some 40 kilometers (25 miles) from Heglig on Friday, the fourth day of the worst clashes since South Sudan's independence last year.

Sudan's army said on Friday it has launched a counterattack towards Heglig town in its main oil-producing region where South Sudanese forces took control earlier this week.

"Now we are moving towards Heglig town" and are "close," army spokesman Sawarmi Khaled Saad said in a statement.

Sudanese warplanes launched their first attack on a major South Sudanese town on Thursday, with five bombs dropped on the capital of the oil-producing Unity border state, Southern officials said.

"They dropped bombs in Bentiu town -- apparently they were aiming for a bridge," South Sudan's deputy information minister Atem Yaak Atem told Agence France Presse.