Opponents of a referendum on independence for south Sudan due next month are threatening lawsuits and spreading confusion to try to disrupt the vote, the chief official running the plebiscite said on Saturday.
Mohammed Ibrahim Khalil, the head of the referendum's organising commission, told Reuters that his staff had been flooded with spurious complaints that all appeared to come from the same group.
Southerners are expected to vote for independence in the politically-sensitive plebiscite which is scheduled to start in just over four weeks' time on Jan. 9 and last a week.
Southern leaders have accused the north's ruling National Congress Party (NCP) of trying to find ways to disrupt the vote to keep control of the region's oil reserves.
The referendum was promised in a 2005 peace deal that ended a north-south civil war. Both sides have accused each other of building up troops close to their border in recent months.
"We have received complaints in identical terms from different parties very clearly instigated by one main source, all of them groundless ... The whole idea is to create confusion and give the idea that something serious is going wrong," Khalil said.
Khalil, a northerner, declined to say who he thought was behind the campaign of disruption.
"It would be completely wrong for me to say. I am completely neutral in this," he said. "It is people who want to sponsor the option of unity and want unity to continue."
State-linked media reported earlier that a group called the Higher Council for Peace and Unity had filed a "constitutional case" against the commission and the south's dominant Sudan People's Liberation Movement (SPLM), saying they had violated the law governing the vote.
The Sudanese Media Centre quoted on Friday the head of the campaign group Puol Lilly as accusing the SPLM of controlling the commission, rigging the registration process and harassing potential voters.
Senior SPLM member Yasir Arman told Reuters this week his party has been expecting legal challenges from groups he said were backed by the NCP. "It is an open secret that the National Congress was preparing the ground," he said.
It was unclear what impact a case would have on the already tight schedule for the referendum. No one was immediately available for comment from Sudan's constitutional court.
International monitors from the United Nations and the Carter Centre have up to now largely praised the commission's organisation of the voter registration process which ended peacefully earlier this week.
Khalil said many of the complaints, including allegations of poor security at registration centres, had nothing to do with the commission, while others were not backed by evidence.
"I don't think there is any legal argument for any constitutional case, not a bit. If somebody wants to obstruct they can always file a petition," he said.
"In case such a petition is accepted ... then the petitioner can easily ask the (constitutional) court to suspend the whole referendum proceedings. That can cause more and more confusion and could plunge the country into problems."