As fourteen Sudanese soldiers were handed over to officials from the International Committee of the Red Cross on Wednesday, an official from South Sudan's ministry of defence General Kuol stated, "It is a goodwill gesture... on a humanitarian basis".

Heavy fighting has raged between the rival armies, with repeated air strikes by Sudanese warplanes inside Southern border area, which South Sudan President Salva Kiir said Tuesday was a declaration of war by Khartoum.

Border regions were reportedly calm Wednesday after days of aerial bombardments that followed the withdrawal at the weekend of Southern troops from the contested Heglig oil field.

Southern troops seized Heglig from Khartoum's army, pulling out 10 days later after international pressure, but said Sudanese warplanes bombed their forces as they moved southwards.

"It is calm now... but it doesn't mean there is no more bombardment—they (Sudan) could do it at any time, as they don't take world orders," Southern army spokesman Colonel Kella Kueth said.

The released prisoners— the first from either side to be released—were captured during the South's seizure of Heglig, a battle in which heavy casualties on both sides were reported.

One of the prisoners, a Southerner who was conscripted into Sudanese army, opted to remain the South, but the remaining 13 are due to be flown via Egypt before going home to Sudan.

"We hope that this process will help in getting the situation calm between Sudan and South Sudan," said Egypt's ambassador Moyad el-Dalie, who is supporting the return of the troops.

"I would also like to assure that the request for the release of soldiers of South Sudan that were captured in Sudan, Egypt is committed to facilitating that."

The Sudanese soldiers arrived by plane in Juba 10 days ago, looking exhausted but with those wounded in battle having received medical treatment.

On Wednesday, the soldiers were dressed in new civilian clothes, and appeared to be in good spirits, an AFP reporter at the handover said.

"I'm happy at the fact that I am released and going home," said one freed soldier, adding he planned to return to the army "and defend my country."