ACCRA, May 28 (Reuters) - South African gold miner Randgold Resources Ltd. is interested in Ghana-based Ashanti Goldfields Co. Ltd. but no formal offer has yet been made, an Ashanti source said on Wednesday.

Ashanti is already in merger talks with South Africa's AngloGold Ltd. A deal would create the world's biggest gold producer, with combined annual output of 7.6 million ounces.

"We are aware that Randgold is interested in Ashanti but we have yet to receive any documents or an official offer," the source said, on condition of anonymity.

The source said Randgold executives were expected in Ghana this week to make a presentation to the Ghanaian government, which holds a 17 percent stake in Ashanti, including a golden share allowing it to veto takeovers.

Ghanaian Mines Minister Cecilia Bannerman told Reuters she was aware of Randgold's interest.

"I've been told; It's been indicated to me that such an interest has been made. But I am yet to be furnished formally with their proposal document," she said.

A spokeswoman for Randgold declined to comment on the reported interest.

"Randgold Resources has frequently said that it is continually evaluating all significant growth opportunities in the gold industry but it does not disclose details of these investigations or comment on market speculation about industry developments," she said.

AngloGold shares closed down 0.6 percent at 243.50 rand in Johannesburg on Wednesday. Ashanti's London-listed American Depositary Receipts closed down 1.36 percent at $7.25. In New York, Ashanti was trading at $7.32 at 1950 GMT.

AngloGold and Ashanti announced the merger talks on May 16. Under the deal, Ashanti shareholders would receive 26 AngloGold shares for every 100 Ashanti shares held.

Sources close to the deal said late Tuesday that AngloGold was prepared to let Ghana's government retain its golden share.

However, under AngloGold's proposal, the government would only be able to invoke its golden share for transactions involving the combined company's Ghanaian assets, one of the sources told Reuters in Ghana.

Ashanti has an annual output of 1.6 million ounces and operates seven mines in Africa. Four of them are in Ghana and their combined output accounts for about 55 percent of Ashanti's total production.

Ashanti also has mines in Guinea and in Zimbabwe and jointly operates a mine in Tanzania with AngloGold.