By MAGGIE FICK | AP

Published: Sep 1, 2010 01:54 Updated: Sep 1, 2010 01:54

JUBA, Sudan: The army of Southern Sudan has been looting food convoys and carrying out other attacks on aid groups, officials of those groups alleged, and a top military officer warned Tuesday that the humanitarian groups could be expelled if the complaints get too "harsh."

The aid community in Southern Sudan documented 80 incidents of obstruction, vehicle hijackings or harassment of aid staff by southern troops since February. No aid staff have been killed, but several have been wounded.

International aid workers are worried that access to needy populations in a region already plagued by hunger may be further restricted as an independence referendum scheduled for January approaches. The vote would determine whether the south splits off from Sudan and forms a separate country. The UN says that 4 million people in Southern Sudan — roughly half the population — rely on food aid to survive.

The Sudan People's Liberation Army, the former rebel group which now forms the army here, denies it is deliberately hindering humanitarian work, but a spokesman acknowledged an incident did occur in Upper Nile state in June in which staffers from the aid group Tearfund were beaten and detained by SPLA soldiers.

Army spokesman Lt. Gen. Kuol Deim Kuol said the southern army believed one of the staff members who was beaten and detained was supplying food and medicine to elements of a militia the army suspects is allied with an opposition party. The spokesman alleged that this militia has ambushed government boats along the Nile River.

"It is not a problem between Tearfund and the SPLA, it is a problem between the SPLA and these wrong elements who are employed in Tearfund," said Kuol.

A Tearfund official in Juba declined to comment, saying the group's director was out of the country. The director did not immediately respond to an e-mail.

Officials from four aid groups said in recent days that that their work is becoming increasingly dangerous. They said they could not speak out publicly because of fears of reprisals from the government and military.

The attacks have raised fears that the southern government has given its troops permission to root out opposition supporters, without any regard for the humanitarian consequences.

The UN's top humanitarian aid official in Southern Sudan said on Monday that humanitarian workers are struggling to distribute food.

"There have been interference with the provision of some of that assistance. We know that this is a matter of concern of the SPLA and we're very pleased that steps are being taken to address that," the official, Lise Grande, said at a news conference.

The military's chief of staff, Gen. James Hoth Mai, said Tuesday that bringing up such issues is the only way to resolve them, but he made what humanitarian workers saw as a veiled warning.

"I said please don't be harsh to us like that because tomorrow we can tell you to quit this country and you can go," Mai said. "But now, for you to continue with your work, you come tell us your problems in a polite way so that you continue with us." The SPLA, a guerrilla movement that fought a 23-year civil war against the Khartoum-based government, is still in the early stages of transformation into a professional army. ¬