United Company RusAl, the world's largest primary aluminum producer, said Thursday that it had agreed to sell 50 percent of two coal mines in Kazakhstan for the $345 million offered in September by state-run Samruk Holding.

"The cost of the stake was calculated by Deutsche Bank through a detailed audit and evaluation of the asset," RusAl said in an e-mailed statement.

RusAl agreed in November to transfer the stake and set up a venture with Samruk to develop the Bogatyr and Severny fields, which make up around 45 percent of Kazakh coal output. Kazakhstan was seeking to buy the stake to supply the nation's coal-fired power stations and planned to pay about $345 million, Samruk said in an e-mailed presentation Sept. 28.

The two companies will boost output 42 percent to 60 million tons per year and sell coal in Kazakhstan and Russia, RusAl said in a Nov. 29 statement. The joint venture, Bogatyr Access Comir, said Monday that first-quarter sales rose 37 percent to a record 13 million tons, buoyed by shipments to Russia.

Bogatyr was previously owned by billionaire RusAl investors Viktor Vekselberg and Leonard Blavatnik and became part of RusAl after the company's purchase of rival aluminum maker SUAL. Kazakhstan has the world's eighth-largest coal reserves.

The venture will be worth $5 billion in seven years, RusAl chief executive Alexander Bulygin said, Interfax reported in November.