* Conflict has afflicted Darfur since 2003
* Worst fighting for months has displaced 130,000 people
* New violence in two parts of vast western region
KHARTOUM, Feb 22 (Reuters) - Fighting re-erupted in the north and south of Sudan's strife-torn Darfur region, tribal and rebel officials said on Friday, after clashes last month that killed hundreds of people and displaced more than 130,000.
Conflict has plagued the vast arid region since mainly non-Arab tribes revolted against the Arab government in Khartoum in 2003, accusing it of political and economic neglect. Violence has ebbed since 2004 but picked up again in recent months.
Heavy fighting broke out in January between two Arab tribes, the Bani Hussein and Rizeigat, over gold in the Jebel Amer area of North Darfur, displacing 100,000 people, according to the United Nations.
Tribal leaders mediated a ceasefire but clashes flared again on Thursday in the El Sireaf area, killing 21 people and wounding at least 33, according to a Bani Hussein leader who asked not to be identified. "Clashes lasted for eight hours after some Rizeigat troops attacked the area yesterday morning."
He said some 500 people had been killed and 128 villages torched since the outbreak of fighting in January. "The situation is very bad," he added.
The government of North Darfur and the Rizeigat tribe could not be reached for comment on Friday, a holiday in Sudan.
The U.N. Office for the Coordination of Humanitarian Affairs (OCHA) said on Thursday it had managed to supply emergency food to El Sireaf and most other affected areas but that the security situation remained a "major problem".
"The number of displaced people in different locations is constantly changing as people continue moving around," OCHA said in a report.
In South Darfur, rebels of a Sudan Liberation Army faction led by Minni Minnawi said they had attacked an army post near Nyala, the region's largest city.
"Government forces fled into the city centre so we managed to seize weapons they left behind," SLA official Nur el-Daim Ahmed said. Army spokesman al-Sawarmi Khalid could not be reached for comment. A resident confirmed fighting in the area.
"The rebels arrived with four cars and attacked the army in an area some 15 km (nine miles) from Nyala where the government presence is weak," said the resident, declining to be named.
Fighting between the army and another SLA faction in the central Jebel Marra area in January displaced 30,000 people.
Events in Darfur are hard to verify as Sudan restricts travel by journalists, aid workers and diplomats. Authorities denied Reuters in January a travel permit to attend a government-sponsored disarmament conference in West Darfur.
The International Criminal Court has issued arrest warrants for Sudanese President Omar Hassan al-Bashir and some aides to face charges of masterminding war crimes in Darfur. They deny the charges and refuse to recognise the court.
Human rights groups and the United Nations estimate hundreds of thousands of people have died in the Darfur conflict overall. The government says around 10,000 people have been killed. (Reporting by Khalid Abdelaziz; Writing by Ulf Laessing; Editing by Mark Heinrich)