BENTIU: Sudanese war planes launched a fresh bombing raid on a key South Sudanese town on Monday, dashing hopes that a withdrawal of Southern troops from a contested area would end weeks of fighting.

Several bombs were dropped on Bentiu, capital of the oil-rich South Sudan border state of Unity, killing at least one child, officials said.

“This is a serious escalation and a violation of the territory of South Sudan... I think it is a clear provocation,” Mac Paul, the South's deputy director of military intelligence said.

The attack, the latest of several on the town and in South Sudan's border state, come a day after the South's army said it had completed a pullout of the contested Heglig oil field, seized from Sudan's army on April 10.

South Sudanese officials said the withdrawal from Heglig had been ordered to avert a return to all-out war after heavy fighting between the rival armies, but added that Khartoum continued to attack, including with air strikes, the departing troops.

“The bridge and the market were bombed... one person was killed and three were injured in the market,” Paul added.

Bombs targeting a key bridge in the town landed some 50 metres away from an AFP reporter, prompting heavy bursts of gunfire from Southern soldiers hoping to shoot down Khartoum's Antonov bomber airplanes.

In the market, stalls were on fire and large plumes of grey smoke rose high into the air, as screaming civilians ran in panic.

Several shouted angrily that the South had been made to withdraw from Heglig, but that the attacks on civilians were still continuing.

One charred body of a small boy was seen by an AFP reporter, while market traders said that three civilians had been killed, although those figures could not be immediately verified.

“Yesterday they (Sudan) attacked us, and then today they continue to attack us, what is next?” said the South's Lieutenant General Obuto Mamur.

Southern officials claimed Sudan's troops had pushed across the contested border on Sunday before being repelled after heavy fighting, although it was impossible to verify exactly where the clashes took place.

Southern troops were digging into positions fearing renewed ground attacks by Sudan, he added.

“We do not attack, but our soldiers are in their positions,” Mamur said.

There was no immediate reaction from officials in Khartoum.

Violence in Heglig was the worst since South Sudan won independence in July after a 1983-2005 civil war in which about two million people died.

The United Nations said Sunday the entire population of Heglig had fled the unrest, with thousands of the displaced civilians living in the open.

The South pulled out from Heglig after international pressure, but is calling on Khartoum to withdraw its troops from the contested Abyei region, which it seized last May forcing 110,00 civilians to flee southwards.

Tensions have gradually mounted over the disputed border and other unresolved issues, raising fears in recent weeks about concerns of a wider war.