Sudan has carried out indiscriminate aerial bombing and other serious violations of international humanitarian law in its South Kordofan and Blue Nile border states, Human Rights Watch (HRW) charged on Wednesday.
The New York-based watchdog called for a United Nations'-mandated investigation and sanctions on those responsible for the alleged violations.
Fighting between ethnic Nuba rebels and government troops in oil-producing South Kordofan broke out in June 2011 and spread to Blue Nile three months later.
More than 900 000 people are estimated to have been displaced or severely affected, according to the United Nations.
"Since the conflict started, Sudanese forces have carried out indiscriminate aerial bombardment and shelling in populated areas, killing and injuring civilians and causing serious damage to civilian property", HRW said in the report based on visits to the two states and to South Sudanese refugee camps.
The watchdog did not have access to government-controlled areas.
"The evidence documented suggests that the Sudanese government has adopted a strategy to treat all populations in rebel-held areas as enemies and legitimate targets, without distinguishing between civilian and combatant," it said.
"This apparent approach lies at the heart of the serious violations of international humanitarian law documented in this report."'
The Sudanese army and foreign ministry could not immediately be reached for comment.
Rebels have admitted shelling the South Kordofan state capital in October and November, in attacks the UN children's fund said killed 18 people.
HRW did not give a casualty estimate from the hundreds of government bombings, shellings and rocket attacks it said have occurred against civilian areas across the rebel-held Nuba Mountains of South Kordofan.
Bombings typically use unguided munitions dropped from high altitude, which does not allow for accurate delivery, it said.
According to one victim cited in the report, bomb shrapnel flew into the opening of a cave where a mother and daughter had sought refuge.
"The shrapnel hit me on the side, until my intestines came out," the mother, Halima Tiya Turkan (35) was quoted as saying.
In Blue Nile, HRW said "scores" of civilians have been killed, maimed or injured by government bombing and shelling, including from "barrel bombs" filled with nails and other jagged pieces of metal.
Sudan accuses South Sudan of supporting its former civil war allies in the rebel SPLM-N, a charge analysts believe despite denials by the government in Juba.
South Sudan became independent in July last year. – AFP