By Hyunjoo Jin

The refining unit of South Korea's SK Innovation is bidding for a stake in Australian petrol and convenience store retailer United Petroleum, the company said on Monday in a statement to the stock exchange.

The privately owned Australian company, which has a value of about A$1 billion ($936 million) including debt, is exploring a sale or a joint venture, sources familiar with the matter told Reuters in July.

SK Innovation said its unit SK Energy had placed a bid for United Petroleum, but gave no further details.

SK's rival S-Oil has also submitted a non-binding offer for a stake in United Petroleum.

The Korea Economic Daily newspaper, citing sources in the refining industry, had reported earlier on Monday that SK Innovation was one of five to six companies that had recently submitted a non-binding offer for the United Petroleum.

The newspaper said the main bidding process was expected to take place in January.