The UN Security Council expressed alarm on Tuesday at recent clashes between Sudan and South Sudan along their disputed border and urged both sides to halt military operations.
The UN warned that the fighting could escalate into a new war.
Sudan and South Sudan blamed each other for the fighting.
South Sudan said its neighbour Sudan launched air strikes on major oilfields in its Unity state on Tuesday, in one of the most serious reported confrontations since the South declared independence from Sudan in July.
"The Security Council calls upon the governments of Sudan and South Sudan to exercise maximum restraint and sustain purposeful dialogue in order to address peacefully the issues that are fueling the mistrust between the two countries," the 15-nation council said in a statement.
South Sudan won its independence under a 2005 peace deal that ended decades of civil war with Khartoum, but distrust still runs deep.
Both sides were still at loggerheads over the position of their shared border and how much the landlocked South should pay to transport its oil through Sudan.
"The Security Council is deeply alarmed by the military clashes in the region bordering Sudan and South Sudan, which threaten to precipitate a resumption of conflict between the two countries, worsen the humanitarian situation and lead to further civilian casualties," 15-nation council said.
Sudan denied launching air strikes but said its ground forces had attacked Southern artillery positions which had fired at the disputed oil-producing area of Heglig that is partly controlled by Khartoum.
"Our armed forces are ready to defend every inch of our territorial integrity whether it's an attack or aggression from the government of South Sudan or the rebel movements," Sudan's UN ambassador, Daffa-Alla Elhag Ali Osman, said on Tuesday.
He told reporters that while the UN Security council statement was not as strong as Khartoum would have liked, Sudan hoped it would "draw the attention of the south to come to their senses and respect the path of peace."
Analysts had long said tensions between the countries could erupt into a full-blown war and disrupt the surrounding region, which includes some of Africa's most promising economies.
The latest violence has already set back efforts to resolve the countries' disputes.
Sudanese President Omar Hassan al-Bashir has suspended talks with his Southern counterpart Salva Kiir aimed at resolving them, state media reported.
UN Secretary-General Ban Ki-moon said he was worried about the fighting, which started on Monday along the border.
The Security Council also voiced concern about South Kordofan and Blue Nile states.
It said council members stressed "the grave urgency of delivering humanitarian aid in order to avert a worsening of the serious crisis in Southern Kordofan and Blue Nile states, Sudan."
Clashes broke out between Sudan's armed forces and rebels of the Sudan People's Liberation Movement-North (SPLM-N) in South Kordofan last June, then spread to Blue Nile state in September.
Both areas border newly independent South Sudan. (Reuters/NAN)