Updated

Six bombs that Sudan maintains were aimed at rebels in its own territory instead landed across the border inside South Sudan, according to a United Nations report.

U.N. observers who visited the site found six bomb craters 1.16 kilometers (.72 miles) inside South Sudan's territory, according to the internal report obtained by The Associated Press on Tuesday. South Sudan officials told the U.N. team that a man who was wounded in the bombing later died.

The timing of the incident is crucial because South Sudan and Sudan are currently meeting in Ethiopia to negotiate outstanding issues from their peaceful split last year. The U.N. Security Council says the issues — including an agreement on the full demarcation of a border and how to share oil revenues — must be resolved by Aug. 2.

After the bombing allegations, the African Union — which is overseeing the Sudan-South Sudan negotiations — said it would investigate. The AU reported that Sudan said its forces attacked a group of Darfur rebels "within the territory of Sudan."

The U.N. team said the six bombs created small craters where they came down in Northern Bahr el Ghazal state early Friday.

"The craters are almost in one line, possibly indicating a bombing run by an aircraft. Bomb fragments and debris was visible in and around the craters. The smell of 'gunpowder' was also evident," the report said.

South Sudan has said the Sudanese military dropped the bombs from Antonov planes.

The U.N. report also said that an Antonov military aircraft was spotted flying over the South Sudan city of Bentiu, in Unity State, on Saturday. South Sudan does not have Antonov planes.

A U.N. spokesman in South Sudan did not immediately respond to a phone call, email or text message seeking comment. A spokesman for the government in Khartoum could not immediately be reached.

The spokesman for South Sudan's military, Col. Philip Aguer, said eight bombs were dropped early Friday morning. He said South Sudan is compiling a record of all the bombs dropped in its territory by Sudan, but that neither the African Union nor the U.N. has taken any action.

"We hope that the AU will take action because Sudan has to be condemned for these hostile attacks against the Republic of South Sudan," Aguer said. "Instead of an escalation of hostile activities we had been expecting security cooperation. Otherwise violent conflict will bring down these two states," he added.

The mostly black African tribes of South Sudan and the mainly Arab north battled two civil wars over more than five decades, and some 2 million died in the latest war, from 1983-2005. It came to a halt with a 2005 peace deal that led to last year's independence declaration for South Sudan.

Though the breakup was peaceful, hostilities flared this year. South Sudan inherited about three-quarters of the region's oil, but the south shut down its oil industry in January after accusing Sudan of stealing oil that the south most pump through Sudan's pipelines. That decision has cost both governments dearly in lost revenue.

In April the two countries' militaries fought over the disputed, oil-rich region of Heglig. South Sudan troops took over the town from Sudanese forces, but that offensive maneuver was condemned by world leaders. South Sudan says it then retreated from Heglig, though Sudan says its forces pushed the south out.

Bombing by Sudanese aircraft over South Sudan were common during the hostilities.

The U.N. Security Council ordered the two sides to hammer out agreements following the April clashes. The May U.N. resolution threatens sanctions against both sides if they did not immediately resume talks and reach a final deal by Aug. 2.