Oxfam, in a Monday statement, said bombing raids and the presence of military forces along the border between Sudan and South Sudan created significant complications to an already troublesome humanitarian crisis.
The aid agency said its staff on the ground in South Sudan reported heavy bombing near a refugee camp. Khartoum denies it was behind the bombing, though both sides have been involved in border clashes since South Sudan's independence in July.
Herve Ladsous, under secretary-general for peacekeeping operations, told members of the U.N. Security Council that both sides needed to work together to avoid an escalation of violence.
"Only the two parties, working together, can efficiently and effectively manage security at their common border, and … the United Nations stands ready to support them in this respect," he said in his statement.
South Sudan's independence was part of a comprehensive peace agreement brokered with Washington's help in 2005. Border demarcation issues, ethnic conflicts and disputes over oil threaten to unravel the peace deal, however.
Ladsous urged both sides to work on concrete solutions to outstanding issues during negotiations scheduled next week in Ethiopia.