South Africa denied Wednesday any corruption was involved in a multi-billion dollar nuclear energy deal after controversy erupted over whether Russia had won the contract.

On September 22, Russia's national atomic energy corporation Rosatom appeared to announce that it had been chosen to develop eight nuclear reactors in South Africa, worth up to $50 billion (40 billion euros).

The announcement, which followed a secretive trip to Moscow by President Jacob Zuma at the end of August, prompted allegations that the government was dodging procurement rules.

The Department of Energy said Wednesday, however, that the pact signed with Russia was simply a preliminary agreement on nuclear cooperation.

"The Russian Federation and South Africa signed an intergovernmental agreement," said acting director-general Wolsey Barnard.

"Similar agreements will be signed with various other countries and vendors in the months to come."

Controversy over Rosatom's announcement intensified after a local newspaper reported Zuma personally negotiated the deal with Russian President Vladimir Putin.

"The procurement process has not started. Therefore, the nuclear programme is not associated with corrupt procurement processes," the department of energy said in a statement.

It said the specifics of the nuclear power plant procurement process -- including the type of tender -- have not been decided.

The preliminary agreements "mark the initiation of the preparatory stage for the procurement process that will be undertaken in line with existing laws and regulations," said Barnard.

South Africa's opposition Democratic Alliance, which had called for parliament to investigate the agreement with Russia, responded sceptically to Wednesday's statement.

"We think that their commitment to transparency about the nuclear programme remains hollow," said shadow minister of energy Lance Greyling.

"They are refusing to release the road map for the nuclear procurement process.

"Their statement that the public will be kept informed of all decisions, that frankly isn't good enough."

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

Heavily dependent on coal for generating electricity, South Africa's has trouble meeting peak energy demand.

North-West University nuclear engineering lecturer Dawid Serfontein said that the nuclear announcement soon after Zuma made the mysterious trip to Russia inspired speculation that the deal was suspect.

"I think the whole thing that President Zuma went to Russia in secret, the next moment he comes back with a nuclear deal, it gave people a suspicion that the tender process won't be followed," said Serfontein, speaking from Johannesburg.