KHARTOUM (Reuters) - More than 60,000 people have fled a town in Sudan's main oil region since it was attacked by insurgents in April, the United Nations said in a report on Thursday.
Rebels said later they had shot down a second military helicopter within one week.
Government forces retook the town of Abu Kershola two weeks ago from fighters belonging to the Sudanese Revolutionary Front (SRF), a rebel alliance seeking to topple President Omar Hassan al-Bashir. Abu Kershola lies in the northeastern tip of the South Kordofan state, home to most Sudanese oil production.
But the SRF struck back, attacking a convoy of Sudan's army chief of staff during a visit last week.
The fighting in Abu Kershola has displaced 63,000 people, the U.N. report said. Some 8,000 people had fled to Khartoum, more than 600 km (370 miles) away, while 44,000 were seeking shelter in the neighboring state of North Kordofan.
"The security situation remains fragile," the report said.
Later in the day, the SRF said that it had shot down an army helicopter in Blue Nile state, another fighting front near Sudan's eastern border with Ethiopia.
Army spokesman al-Sawarmi Khalid dismissed the rebel assertion, saying a helicopter had crashed on a training mission in the state capital Damazin after hitting an electricity tower. Two persons died, he said.
It was impossible to verify the conflicting statements.
On May 31, the army said an aircraft had crashed near Abu Kershola for technical reasons. The SRF said then that it had downed a helicopter in the area.
For decades Sudan has been plagued by clashes between the government and rebels fighting against what they say is exploitation by a Khartoum elite.
The SRF is made up of three rebel groups from Darfur and the Sudan People's Liberation Movement-North (SPLM-N), fighting along the border with South Sudan.
The violence has strained relations with South Sudan, which Sudan accuses of backing the rebels. Juba denies this.
The unrest is a sensitive topic in Khartoum. A journalist working for the daily al-Sudani newspaper was arrested after the army accused him of damaging its reputation, his lawyer said.
Khalid Ahmed had written a report on Abu Kershola after visiting the area with the chief of staff.
(Reporting by Ulf Laessing and Khalid Abdelaziz; Editing by Mark Heinrich)