A statement issued by the rebel movement on Tuesday accused the Sudanese authorities of violating international resolutions and ceasefire agreements signed between the two sides.
The rebels accused the Sudanese government of trying to obstruct the constituent conference of the SLM inside the "liberated lands".
Earlier, the SLM said the government had killed 10 of its fighters and at least 10 civilians, adding that the attacks were aimed at derailing peace talks to be held this week in Abuja.
A spokesman for the Sudanese armed forces said government forces were not involved in any attacks in Darfur.
Meanwhile, a severe jet fuel shortage has forced the UN World Food Programme to cut its deliveries to southern Sudan by half at the height of the hunger season.
The WFP said in statement released in Khartoum on Tuesday that it had delivered 10,600 tonnes of food to southern Sudan in August, mainly by road from Kenya and Uganda.
Its goal had been 20,700 tonnes for 1.3 million people.
"This is a tragedy for hundreds of thousands of people," said Ramiro Lopes da Silva, WFP director in Africa's largest nation.
"This could not have happened at a worse time for the people of Sudan," he added.
The WFP is concerned about growing malnutrition in parts of southern Sudan ahead of the coming harvest, pointing out that more than 1100 of the children are considered to be severely malnourished.
The shortage of jet fuel at WFP's main air hub in El Obeid was the main problem, WFP said, cutting capacity to move food by air.
For example, it only delivered 1678 tonnes by air from El Obeid to the south in August compared with a target of 11,692.
"This could not have happened at a worse time for the people of Sudan"
Ramiro Lopes da Silva, WFP Sudan director
The fuel shortage, which has gone on for several months, was blamed on insufficient contributions and late arrival of donor funds, as well as slow deliveries of fuel, a shortage of tankers, limited storage and high demand.
The WFP urgently appealed for donors to send their promised aid.
The statement said the Emergency Operation for the South, East and Transitional Areas had a shortfall of 41%, or $124 million, so far this year.
The closure in July of Sudan's only refinery that produces the jet fuel also hurt the situation, the statement said.
The refinery's closure, for repairs, also affected the African Union, which suspended peacekeeper deployments to Sudan's war-torn Western Darfur region due to lack of jet fuel and heavy rains.
The WFP appealed for donors to
send their promised aid urgently
"Supplies of JetA1 [fuel] were short even before the refinery closure," Lopes da Silva said.
"That pushed us over the edge. We tried everything we could to get sufficient supplies in time, but the demand was simply too great."
He admitted that flying the food to the sites was costly but necessary due to the rainy season and lack of roads in the south.
The statement said the shortage of jet fuel continued into September and also hampered deliveries of food aid to Darfur.
The statement cited statistics from non-governmental organisations in Northern Bahr El Ghazal province that showed more than 8500 malnourished children are in feeding centres supplied with an enriched corn-soya blend by the WFP.