The army of southern Sudan said northern forces have attacked one of its bases in an effort to derail the south's coming referendum on independence.
A spokesman for the southern army, Philip Aguer, said helicopter gunships from the north carried out the attack Wednesday, injuring four soldiers and two civilians. He said the northern army, the Sudan Armed Forces, is trying to disrupt the referendum process.
Reuters news agency quotes a northern army spokesman, al-Sawarmi Khaled, as saying the accusation is "absolutely not true." The spokesman said the SAF has not attacked anywhere near the north-south border.
If confirmed, this would be the second time this month northern Sudanese forces have carried out an airstrike in the south. On November 13, northern aircraft bombed the south while fighting rebels from Sudan's Darfur region. Northern officials said the bombing was an accident.
Officials of northern Sudan's ruling National Congress Party have accused the south of supporting the main Darfur rebel group, the Justice and Equality Movement. In interviews this week, senior NCP official Mandour al-Mahdi said the alleged support is a "declaration of war" against the north.
Tensions between Sudan's Khartoum-based government and the semi-autonomous south have been rising as the south's January 9 vote on independence draws near. The oil-rich Abyei region is scheduled to vote the same day on whether to be part of the north or the south.
Disputes over borders, voter registration, and oil revenue sharing have left planning for both referendums far behind schedule. President Omar al-Bashir and southern leader Salva Kiir met Tuesday with East African leaders in Ethiopia in an effort to resolve the issues.
The two referendums are part of the 2005 peace agreement that ended Sudan's 21-year north-south civil war.
Some information for this report was provided by AFP and Reuters.