BEIJING - The Sinopec Group, Asia's top oil refiner, said Saturday it will buy a 25-percent stake in a nitrile butadiene rubber (NBR) plant belonging to leading Russian petrochemical company SIBUR.

The Sinopec Group signed an agreement with SIBUR on Saturday to expand the annual output capacity of the NBR plant in Krasnoyarsk to 56,000 tons from the current 42,000 tons, according to a press release issued by the company.

It said the two firms plan to establish a joint venture company at the end of this year.

An oil-resistant synthetic rubber, NBR is widely used in aeronautics and astronautics, as well as in the oil, petrochemical and textile industries.