The United States and Canada say they are "appalled" by aerial bombing, which Sudan reportedly carried out near a hospital in war-torn South Kordofan.
"We strongly condemn any targeting of civilians, and are appalled by this attack on those providing essential medical care or humanitarian assistance to people in need," embassies of the two North American nations said in a joint statement.
"International humanitarian law obligates all parties to a conflict to distinguish civilians from combatants."
The statement said a number of bombs were reportedly dropped by Sudan's air force near the Mother of Mercy Catholic Hospital in the Nuba Mountains of South Kordofan state on May 1-2.
Some people were injured while patients and staff were terrified, it said.
Sudan's armed forces spokesman Sawarmi Khaled Saad told AFP the incident did not occur.
"We didn't bombard any hospital or target any civilians," he said.
