DUBAI, Oct 30 (Reuters) - Sudan's Rapid Support Forces (RSF) said on Monday they had seized an airport west of the capital from the army and workers at an oilfield said they were evacuated due to the attack as the warring factions reconvened for talks in Saudi Arabia.

The RSF said Belila airport in the state of West Kordofan had been used by the army, which it has been fighting since mid-April, to launch warplanes. Employees at Belila oilfield, which produces much of Sudan's meagre and dwindling oil output, said they were evacuated on Sunday night because of the fighting.

The two sides have also been battling in the western cities of El Obeid and El Fasher in recent days, as U.S.- and Saudi-sponsored talks that aim to broker a lasting ceasefire restarted on Sunday in the Saudi city of Jeddah.

The war in Sudan began after the army and RSF, which previously shared power after leading a coup, came to blows over plans for a transition towards elections and the integration of their forces.

The war has caused a major humanitarian crisis, displacing nearly 6 million people, killing thousands, devastating the capital Khartoum, and triggering ethnically driven killings in the western region of Darfur.

The RSF, which has its power base in Darfur, has been fighting to secure control of key infrastructure and routes in the west of the country in an effort to cut off army operations.

Last week it said it had seized Nyala, Sudan's second largest city and the capital of South Darfur.

One Nyala resident said the army had continued with air strikes - utilising its main advantage in the war - even as the RSF was taking over its main base in the city.

The Sudanese army and oil ministry did not respond to requests for comment.

(Reporting by Khalid Abdelaziz, writing by Nafisa Eltahir; editing by Aidan Lewis)

((Nafisa.Eltahir@thomsonreuters.com;))