Soldiers from Sudan and South Sudan clashed at a river dividing their two countries, leaving 22 dead as fighting spread to a new area of the tense border. A Sudanese official demanded on Wednesday that South Sudan withdraw from an oil-rich area it occupied last week or face a concerted attack.

Tuesday's firefight began after a Sudanese soldier shot a South Sudan soldier who was getting water from the river, South Sudan government spokesman Barnaba Marial Benjamin said Wednesday. In all, seven South Sudan soldiers and 15 Sudan soldiers died near the town of Meiram, along the border with Sudan's South Kordofan state and South Sudan's Northern Bahr el Ghazal state, he said.

Even as border violence was spreading to new regions, Benjamin labeled the fight as a "misunderstanding" and said he did not think violence would continue there.

The river battle comes amid wider violence along the shared border around the oil town of Heglig, which South Sudan troops took control of last week. Sudanese aircraft have been bombing South Sudan's Unity State as a part of that fighting.

Benjamin said there was no new fighting around Heglig on Wednesday. But a Sudan official, Mustafa Osman Ismail, warned South Sudan that it must immediately withdraw from Heglig or face counterattacks. Ismail, a senior adviser to Sudan President Omar al-Bashir, spoke in Ethiopia's capital, where he met with Prime Minister Meles Zenawi and African Union officials.

He said the trip was intended to "ask those with influence" to persuade South Sudan to withdraw from Heglig.

Sudan President Omar al-Bashir called several heads of states and sent his foreign minister to South Africa to work on the issue, Ismail said.

"Time is running short, and our army is also getting ready," said Ismail.

He said Khartoum is under pressure from Sudan's public to liberate "the invaded territory" after South Sudan TV broadcast images of what he said are medical staff captured in Heglig.

South Sudan broke away from Sudan in July after decades of civil war, creating the world's newest country. But the two never agreed on how to share the oil wealth found in the region between the countries, and the border was never fully demarcated.

Fighting has intensified in the last several weeks amid fears the two sides could return to an all-out war.


Associated Press writer Kirubel Tadesse in Addis Ababa, Ethiopia contributed to this report.