Randgold Resources Ltd. (GOLD) Thursday said it has made a rival offer for Moto Goldmines Ltd. (MGL.T) in a deal that values the gold exploration firm at about CAD546 million ($488 million).

The deal would give it and AngloGold Ashanti Ltd. (AU) access to one of Africa's largest undeveloped mineral resources, the Moto Gold Project in the Democratic Republic of Congo.

AngloGold, Africa's largest producer of the precious metal, has agreed to part-fund the acquisition in exchange for an indirect 50% stake in Moto, and separately said it will pay $244 million after Randgold closes its deal.

Perth, Australia-based Moto in June agreed to a CAD513 million all-share acquisition by Red Back Mining Inc. (RBI.T), another Africa-focused mining firm with operations in Ghana and Mauritania.

Randgold, which is incorporated in the Channel Islands and mines in west Africa, said its offer represents a 7% premium to Moto's share price as of Wednesday and an 11% premium to the price ahead of the Red Back deal being announced. It said it also has the support of Congo's government, which has a 30% interest in Moto's key Moto project through state-owned Offices des Mines d'Or de Kilo-Moto.

Randgold said it is offering the equivalent of CAD5 a share for Moto, which would be paid with 0.07061 of a Randgold share for each Moto share or a cash alternative. The company could issue as many as 3.9 million shares, it said.

Neither Moto nor Red Back was immediately available to comment. Moto's board has backed Red Back's offer and agreed to pay a break fee of CAD15.25 million to the Canadian company in certain circumstances, and has granted Red Back the right to match competing offers.

At 1230 GMT in London, Moto's shares were up 17 pence, or 6.5%, at 271 pence, and Randgold's were down 35 pence, or 0.9%, at 3836 pence. AngloGold was down 1.2% at 296.50 rand, in line with its peers in South Africa.

Johannesburg-based AngloGold said it would buy half of Moto for cash, and has also agreed to form a joint venture with Randgold to operate the Moto project, which has a mineral resource of roughly 22.5 million troy ounces and is at an advanced stage of exploration.

"Our agreement to acquire for cash a 50% joint venture interest on closing enables Randgold Resources to present terms to Moto which make its offer clearly superior to those already offered by Red Back Mining," said AngloGold Chief Executive Mark Cutifani.

AngloGold, which in 2003 beat out Randgold to buy Ashanti Goldfields Co., and Randgold each own 40% stakes in the Morila gold mine in Mali. The government there owns the remainder.

-By Robb M. Stewart, Dow Jones Newswires; +27 11 783 7848; robb.stewart@dowjones.com

(Jeffrey Sparshott in London contributed to this article.)