A March 16 letter from Sudan's minister of petroleum, seen by Reuters, declared force majeure on deliveries of oil through the pipeline to a terminal near Port Sudan on the Red Sea coast.

The letter said gelling had restricted flows on Feb. 10, and that after this was cleared a major rupture occurred at another point in the pipeline.

The letter said both incidents occurred in areas affected by fighting, and that communications had been hampered by network outages that spread across Sudan in recent weeks.

The quantity of oil affected and resulting loss of revenue from the stoppage were not immediately clear.

South Sudan had been sending about 150,000 barrels per day of crude through Sudan for export, under a formula established when South Sudan gained independence from Khartoum in 2011, taking most oil production with it.

The exports are an important source of revenue for South Sudan, and Sudan takes a cut of the oil as a transit fee.

The official Sudanese sources, who spoke on condition of anonymity and are aligned with the army, blamed the RSF for the stoppage, saying it took place in RSF-controlled territory.

An RSF media official denied that the force was responsible and said that it respected the agreement for oil exports between Sudan and South Sudan.

The letter from Sudan's petroleum minister said resolution of the gelling issues required pumping and heating stations to be fully functional and for adequate supplies of diesel, issues that were "challenged by the current war conditions in Sudan".

The ministry of petroleum in Juba, the capital of South Sudan, did not respond to requests for comment.

The Petrodar pipeline, set up by a consortium including China's CNPC and Sinopec as well as Malaysia's Petronas, runs more than 1,500 km (932 miles) from the Melut Basin in South Sudan's Upper Nile state to Port Sudan on Sudan's Red Sea coast.

Another pipeline carries oil from South Sudan's Unity State to Port Sudan.