South Sudan’s President Salva Kiir, on a visit to China, has told his hosts that Sudan has declared war on his country.
Sudan is among China’s key client states in Africa.
For his part President Hu Jintao insisted Beijing wanted peaceful relations between Khartoum and Juba, and urged “give and take” in the two nation’s affairs.
South Sudan says its oil-producing Unity State came under air attack again on Tuesday, although Sudan says its air force conducted no operations.
However Sudanese president Omar Hassan al-Bashir says the South Sudanese government only understands the “language of the gun” and has been visiting the Heglig area.
A Monday air attack on a market in Bentiu that killed at least two people drew condemnation from UN Secretary General Ban Ki-moon who called on Sudan to stop all hostilities immediately.
Sudan claims the occupation of the disputed Heglig oilfield by the South Sudanese army that ended on Friday is the cause of the uptick in tension.