JEM leaders withdrew from peace talks with the government last May accusing the army of continuing attacks [AFP]
Fighters from the Justice and Equality Movement (JEM), Sudan's main rebel group, have engaged in fresh clashes with security forces as the rebels ambushed a food and supplies government convoy in southern Darfur.
The fighting that erupted on Wednesday between the two sides was the first in months.
Conflicting reports on the death toll have emerged, and the country's ministry of interior said that the police force killed "many" JEM fighters and "suffered only several losses" in the clashes, without giving specific figures.
"The rebels attacked a commercial convoy and the Central Reserve Police protecting the convoy engaged them, suffering several losses," the ministry said in a statement.
But Ali Alwafi, a JEM spokesman, told reporters that at least 50 police were killed, while "three of JEM's members were injured in the combat, none of them seriously".
He also said that the group "captured 13 vehicles [from the government convoy] and destroyed many more".
However, police insisted that none of the convoy's contents were taken and that troops were pursuing them.
Suleiman Sandal, JEM's chief commander, who also reported scores of police casualties, told Reuters news agency that Wednesday's attack was carried out in retaliation to an earlier attack by government troops in the eastern side of South Darfur.
JEM leaders halted their participation in the latest round of peace talks with Sudan's government, which was hosted in Doha, the Qatari capital, last May.
They accuse government troops of continuing attacks on the group in Darfur despite a deal aimed at a cessation of hostilities, signed in February.
Last week, the rebel group released several statements saying that the government was mobilising troops in the western region in preparations to launch a major attack on its strongholds.
Fighting in Darfur, which began with a 2003 rebellion by numerous groups that accuse the government of mistreatment, has killed up to 300,000 people and displaced 2.7 million from their homes, according to UN figures.