|Thousands of people have been displaced by the fighting in Abyei [EPA]
Renewed shelling between northern and southern Sudanese troops in the disputed region of Abyei has forced aid workers to evacuate the town of Agok, located in the area's southern tip.
"This morning, from about 10am, there was shelling on both sides of the river. Later there was shelling just a little bit north of Agok ... All humanitarians are being pulled out of Agok," a humanitarian official told the Reuters news agency on Friday.
The southern army said it had clashed with northern troops in the area, but it was not immediately clear if that was connected to the reported shelling near Agok.
A spokesman for the northern military was not immediately available to comment.
The country's south is just over three weeks away from declaring independence, but Khartoum and Juba have yet to decide who should control Abyei region, raising fears the two sides could return to open conflict.
Khartoum seized Abyei's main town on May 21, pushing as far south as the Kiir River, known as Bahr al-Arab in the north. The waterway has since become the front line between the two sides.
Negotiators from both sides have been meeting in neighbouring Ethiopia since Sunday. Despite reaching an
agreement "in principle" to demilitarise Abyei, no final deal has emerged yet.
The latest reported battles come after the southern military said it exchanged fire with northern forces in Abyei on Wednesday. The northern army denied the report, suggesting internal southern rebel militias may have been behind the clashes.
Thousands of northern and southern residents have been displaced by the fighting.
Southerners voted for independence in a January referendum promised in a 2005 peace agreement that ended a long and brutal civil war. At least two million people died in that conflict.