SK Energy, South Korea's largest oil company, said it will buy a 35 percent stake in a joint petrochemical project with Sinopec in Hubei province.

The two companies signed a framework agreement to form a joint venture, SK Energy said in a statement.

The plant, located in Wuhan in Hubei, will have an annual capacity of 800,000 tons. It is already under construction and will come onstream by the end of 2011, said the statement.