The mining sector in the tiny, landlocked economy was thrust into prominence last month when the United States said it was one of those it was considering to diversify its sources of rare earths following a trade spat with China.

"The mining sector is now bringing more than 50% of the foreign currencies. It will contribute even more, up to 70% in the future. The mining sector contributes more than coffee and tea put together," Léonidas Sindayigaya, the mining ministry's spokesman, told Reuters.

Operators in the sector include Rainbow Rare Earths Ltd .

Exports of gold, tin, tungsten, tantalum and rare earths minerals brought in $12.4 million in the past three months, he said. He did not say how much coffee and tea exports made during the same period.

The government plans to invest in a laboratory to support rare earths miners with research, Sindayigaya said.

Critics, however, accuse the government of failing to ensure that the benefits of the mining sector are spread beyond well-connected elites.

Gabriel Rufyiri, the head of non-governmental organisation Anti-corruption and Economic Malpractice Observatory (OLUCOME), said the sector needed reforms to spread around the wealth to more people, without providing details.

The country also holds nickel deposits, which have not been exploited due to lack of adequate electricity and other infrastructure, mining experts say.