Zimbabwe is considering a ban on raw platinum exports in a bid to force miners to set up refineries in the country, but this move will not take place "overnight", a government official said on Wednesday.

The southern African country has the second largest known platinum reserves in the world, after neighbouring South Africa, and the top two global producers, Anglo American Platinum and Impala Platinum, have operations there.

Both Amplats and Implats currently send platinum concentrate from their Zimbabwean mines to South African refineries but the Zimbabwe government has over the years tried to encourage the firms into processing the metal locally.

Deputy Mines Minister Gift Chimanikire told Reuters that the government, which restored a ban on raw chrome exports earlier this year to promote local smelting, was now focusing on platinum producers.

"They need to start investing in a refinery in Zimbabwe. We need value-addition for our minerals here, we cannot keep exporting jobs," Chimanikire said.

"We're not saying it's going to be overnight. We're ringing the alarm bells to show we're not sleeping."

Platinum producers have said Zimbabwe's current production is insufficient to sustain a viable refinery. Implats' Zimplats operations currently operates the largest mine in the country, with production capacity of 180,000 ounces annually.

Mimosa, Implats' 50:50 joint venture with Aquarius, accounted for more than 20 percent of Aquarius's total attributable output of 487,404 PGM ounces for the full year, while Amplats' Unki mine produced 22,000 ounces in the first half of 2011.

Industry players have talked up the possibility of a refinery being set up in the country five years from now, when the major producers are expected to have ramped up output.

Chimanikire says the government would want to see definite steps towards that target.

"I'm not arguing with that. Let them demonstrate to us that in five years' time, that will happen."