"SPLM-North shelled Kadugli with Katyusha (rockets)," Radio Omdurman said in a brief SMS dispatch citing the state's governor.
A resident of Kadugli told AFP several rockets hit the southern part of the town at about 1500 GMT.
"I saw one house ablaze," said the witness, who had no information about any casualties and asked not to be identified.
The attack came after African Union-mediated peace talks in Ethiopia adjourned yesterday having failed to make progress in halting the nearly three-year-old war in South Kordofan and Blue Nile.
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Talks are supposed to resume later this month.
In Addis Ababa on Monday, the head of the rebel delegation, Yassir Arman, said Khartoum wants "to freeze this war without giving any solutions to the humanitarian situation and the political situation".
The government accused the Sudan People's Liberation Movement - North of raising issues unrelated to the two war zones of South Kordofan and Blue Nile.
Rebel spokesman Arnu Ngutulu Lodi told AFP he had no information about an attack on Kadugli.