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.

"We are going to liaise with the Red Cross to see if they are willing to facilitate their return home," Aguer said, adding that while Southern troops were holding other prisoners of war, he did not have details at present of how many.

Aguer said the South's army remained in control of Heglig, despite a counter-attack launched Friday by the Sudan Armed Forces (SAF) to regain control of the oil field, which consists of around half of Khartoum's oil production.

On Saturday, Khartoum army spokesman Sawarmi Khaled Saad said Sudanese troops were within kilometres (miles) of the main town in Heglig.

However, Aguer reported fresh clashes Sunday in a new area -- a widening of the border fighting outside Heglig -- near to the village of Kuek in the South's Upper Nile state, but that SAF troops had been pushed back.

"We control Heglig... SAF this morning attacked Kuek but they were repulsed," Aguer said.

It was not possible to independently verify the claims, but Kuek is another contested area, on the border with Sudan's White Nile state.

The latest hostilities are the worst since South Sudan's independence from Sudan last July under a 2005 peace accord and have brought the two former foes the closest yet to a return to outright war.

The 14 Sudanese soldiers arrived by airplane in Juba, looking exhausted but apparently well fed and in good spirits, with those wounded in battle having received medical treatment, according to an AFP reporter.

Several had fresh bandages over bullet wounds, others were carried on stretchers.

Captured Sudanese medical officer, Lieutenant Khalid Hassan Ahmed, appeared tired but smiled as he arrived.

"Things are OK... I was brought to treat wounded people where there was fighting, but then we were captured last Tuesday during the attack," he said.

"I was forced to come to fight (for the Sudanese army), I have two bullets in my leg," said Moror Malik, another prisoner.

Some two million people died in Sudan's 1983-2005 civil war, one of Africa's longest, before the peace deal opened the way to South Sudan's independence.