South Africa's government on Tuesday said it had not yet awarded Russia a deal worth as much as $50 billion to develop eight nuclear reactors, saying the countries had merely signed a cooperation agreement.

Russia's atomic energy agency on Monday announced that it had won a lucrative contract to develop nuclear power in South Africa, prompting allegations that President Jacob Zuma's government had dodged procurement rules.

Pretoria's energy ministry insisted Tuesday that the Russia deal "initiates" the "procurement" phase of the project and that other countries would be given a chance to bid.

"Similar agreements are foreseen with other vendor countries that have expressed an interest in supporting South Africa in this massive programme," the ministry said.

"If chosen, all nuclear vendor countries have technologies of their choice that they would want to deploy," a statement said, mentioning a delegation will visit France shortly.

Following the Russian announcement, South Africa's opposition Democratic Alliance called for parliament to investigate.

"The current radio silence observed by the state is cause for serious concern as to whether proper process was followed in formulating and concluding the agreement," the party said in a statement.

South Africa, the continent's most industrialised nation, currently has only one nuclear power plant.

It is heavily dependent on coal for its energy supply and its electricity capacity is already near the maximum.