Pagan Amum, the secretary-general of the ruling party in South Sudan, accused ruling authorities in Khartoum of backing an armed militia in the south. A spokesman for the Sudanese armed forces, however, said the accusations were meant as a coverup for support of rebels in Darfur, the Sudan Tribune reports.
Both sides have traded accusations over support for rebel groups in the country.
Voters recently backed a referendum that was part of a comprehensive peace agreement reached in 2005. Conflict in South Sudan, however, has increased in the weeks following the historic vote.
Fighting broke out last week along the de facto border between North and South Sudan. Officials in the south said the death toll hovered at around 200 people.
The clashes involved members of the South Sudan army and forces loyal to breakaway Gen. George Athor. Athor last year staged an uprising against the government in Juba after losing a state election but agreed to a cease-fire in time for a referendum on secession last month.