South Sudan's military says Sudanese forces killed 17 civilians from the south during the second day of airstrikes Thursday in a disputed border area.
A South Sudan military spokesman said the people killed in the Western Bahr al-Ghazal state were cattle herders.
Officials in Khartoum deny the accusation.
In a separate statement, Sudan's Foreign Ministry alleged that 350 members of a Darfur-based rebel group, the Justice and Equality Movement (JEM), had crossed into South Sudan Wednesday. It said the government has filed a complaint with the United Nations Security Council and the African Union, urging that these combatants should be disarmed and returned to Sudan to face justice.
The statement claims that the rebel forces looted Sudanese villages and abducted 500 citizens from the places they had attacked.
South Sudan seceded in July and became an independent state under a 2005 agreement aimed at ending the north-south conflict. But the two sides have unresolved issues regarding oil-rich Abyei region and the distribution of oil revenue.