A spokesman for the Sudanese government in Khartoum, however, claimed the north was acting in self-defense and denied that Sudan had bombed the South.
U.S. officials condemned the aerial bombardments and supported assertions made by southern officials that these attacks occurred inside South Sudan.
White House spokesman Jay Carney said Sudan must immediately halt the aerial and artillery bombardments.
“They are causing casualties all over the place, and they are obviously gross violations of international law, and we continue to call for an immediate cessation,” she said.
South Sudan became independent from Sudan on July 9 last year. Since then, the two neighbors have had a tense relationship exacerbated by a failure to define a common border and by a dispute about the distribution of the South’s oil.
South Sudanese troops this month seized control of the oil-rich Heglig region, north of the disputed border. Western officials accused the South of escalating tensions.
South Sudanese officials said their actions were justified and that Sudanese troops were using Heglig as a base to attack targets in the South.
On Friday, Mr. Kiir bowed to international pressure and announced that his troops would withdraw from Heglig within 72 hours.
Sudanese President Omar Bashir claimed victory and called his neighbors in the South “insects.”
In a visit to the border region Monday, he vowed not to negotiate with South Sudan “because they don’t understand anything but the language of the gun and ammunition.”
A spokesman for the Sudanese Foreign Ministry in Khartoum said his country had no intention of starting a war with South Sudan and denied that Sudanese armed forces had bombarded territory in the South.