Khartoum - Sudan on Sunday warned South Sudan against damaging oil facilities in the Heglig region it has occupied, after the South accused Khartoum's air force of bombing the area.

“If the South Sudanese army affects the oil infrastructure it means it is keen on taking the conflict to a new level,” Foreign Ministry spokesman Al-Obeid Meruh said in a statement.

South Sudan's army spokesman Colonel Philip Aguer told reporters earlier on Sunday that Sudanese planes were bombing the Heglig area “indiscriminately” but had not managed to oust his country's forces.

Sudan's army claimed on Saturday to be “kilometres” from the main town of Heglig after beginning a counterattack. The army spokesman did not answer phone calls on Sunday.

“We deny that Sudan bombed the oil infrastructure in Heglig,” Information Minister Abdullah Ali Massar said in a statement on the official SUNA news agency.

He said his country also had no wish to bomb oil facilities in South Sudan.

Khartoum tightly restricts the movement of journalists, aid workers and diplomats in South Kordofan state, of which Heglig is a part, making verification of the situation on the ground difficult.

World powers have urged restraint after heavy fighting began with waves of aerial bombardment hitting the South, whose troops on Tuesday seized Heglig from Khartoum's army.

It is the most serious fighting since last July when South Sudan separated after an overwhelming “yes” vote under a peace deal that ended 22 years of civil war.

When the South became independent Khartoum lost about 75 percent of its oil production and billions of dollars in revenue, leaving the Heglig area as its main oil centre.

Tuesday's attack caused a total production shutdown, said Ahmed Haroun, the South Kordofan governor.

The latest fighting follows clashes around Heglig that began on March 26.

After that unrest a Sudanese oil engineer said the area's normal daily output of 60 000 barrels - about half Sudan's total - had fallen to 40 000 because some wells were affected by the fighting. Sudan's oil minister denied there was any damage.

South Sudan disputes that Heglig is part of the north's territory. - Sapa-AFP