Russia called on OPEC to limit oil output rises from its members Libya and Nigeria in the near future, as it hosted a meeting of key OPEC states on Monday to discuss ways to prop up oil prices.

OPEC has agreed with several non-OPEC producers led by Russia to cut oil output by a combined 1.8 million bpd from January 2017 until the end of March. But OPEC states Libya and Nigeria are exempt and their production has been rising.

The deal to curb output propelled crude prices above $58 a barrel in January but they have since slipped back to the $45 to $50 range as the effort to drain global inventories has taken longer than expected.

Rising output from US shale producers has offset the impact of the output curbs, as has climbing production from Libya and Nigeria, which were granted an exemption from the cuts to allow their industries to recover from years of unrest.

Russia's energy minister Alexander Novak said on Sunday that Libya and Nigeria were approaching the moment when their output should be capped due to significant rises in recent months.