By Leos Rousek

PRAGUE--Unipetrol AS (BAAUNIPE.PR) Thursday said it has agreed to buy out the entire stake held by a unit of Eni SpA. (ENI.MI) in a Czech crude oil refinery for 30 million euros ($40.8 million) in a transaction that put the Czech petrochemical company in full control of refining capacities in the country.

In a statement, Unipetrol said it is taking over all 32.445% shares of Eni International BV in Ceska Rafinerska AS, boosting its stake in the oil refiner to 100%.

Late last year, Unipetrol bought out a minority stake in the refiner held by a unit of Royal Dutch Shell PLC (RDSB.LN) for $27.2 million. Shell used to own just over 16% of the Czech refiner.

While Shell has remained committed to the Czech market through its gas station network, Eni is selling its Czech distribution network to the Slovak unit of Hungary's MOL Nyrt. (MOL.BU).

Unipetrol already dominates the Czech gasoline retail market through its gas station subsidiary Benzina AS. Ceska Rafinerska supplies refined oil products to virtually all other gas station networks in the country.

"Further integration of the refining and petrochemical segments remains at the core of our strategic objective," Unipetrol Chief Executive Marek Switajewski said in a statement.

Unipetrol, which is majority owned by Polski Koncern Naftowy Orlen SA (PKN.WA), or PKN, is eyeing buying stakes in local state-owned fuel storage facilities and operators of pipelines for oil products and crude oil. The Czech government is mulling a merger of these companies before evaluating the merged entity's possible privatization.

Write to Leos Rousek at leos.rousek@wsj.com, @LeoRousek

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