Forces from Sudan and South Sudan have clashed in their disputed border region, a day after both sides accused each other of attacks in the oil-rich Heglig area.

The fighting Wednesday comes as the United Nations Security Council prepares to hold a closed-door session to discuss the situation in Abyei, another contested region.

Sudan and South Sudan have been at sharp odds about issues stemming from the south's independence last July, including borders, the sharing of oil revenue and the status of nationals in each other's territory.

The north has accused the south of supporting rebels in the states of Southern Kordofan and Blue Nile, while the south says the north has conducted repeated air strikes, some near refugee camps.