UNITED NATIONS - UN Secretary-General Ban Ki-moon said here on Thursday that the South Sudan's seizure of an oil field in neighboring Sudan is "a clearly illegal act," which he said is "an infringement on the sovereignty of Sudan," and called on "both sides to exercise maximum restraint, return to the negotiation table and resolve their differences."
The secretary-general made the statement at a press conference at a time when Sudanese President Omar al-Bashir on Wednesday declared war and vowed to bring down the government of South Sudan amid escalating military confrontations on the border between the two countries.
"I call on South Sudan to immediately withdraw its forces from Heglig," Ban said. "This is an infringement on the sovereignty of Sudan and a clearly illegal act."
"I urge both sides to exercise maximum restraint, return to the negotiation table and resolve their differences," he said.
Clashes have spread along the border between Sudan and South Sudan, reports said on Monday. The conflict is the closest the two countries have come to a full-scale war since the south seceded from the north in July 2011.
South Sudan and Sudan have been locked in disputes with the alarming situation being manifested most recently by the seizure and occupation of the town of Heglig and its oil fields in Sudan by South Sudan's army, the SPLA.
The United Nations and the African Union have called on South Sudan to withdraw from the town of Heglig, but Juba insists it has a claim to the territory. Sudan has threatened to retaliate.
"I also call on the government of Sudan to immediately stop shelling and bombing South Sudanese territory and withdraw its forces from disputed territories, in particular Abyei," a border town, he said. "Both must stop supporting proxy forces against each other."
"Again, this is not the time for war," he said. "This is a time for leadership, for engagement, for negotiation -- in the name of humanity, and in the interests of the people of both countries and the region."
"Along with regional and many international leaders, I have impressed on both governments the necessity of ending the fighting and returning to negotiations," he said. "They have yet to heed our call."
"We shall continue our efforts and stand ready to help both parties," he said. "Those countries that have influence on the two governments must step up their efforts at this critical moment."
Fresh clashes reportedly erupted on Wednesday near the town of Aweil, South Sudan, some 160 km west of the Heglig oil field near the border between the two countries, which have been seized by the South Sudanese army since April 10.
The oil-rich Heglig region is on the north side of the 1956 border between Sudan and South Sudan.