The increase in OPEC's oil output in April undershot the rise planned under a deal with allies, a Reuters survey found, as declines in Libya and Nigeria offset supply increases by Saudi Arabia and other top producers.

OPEC pumped 28.58 MMbbl/d in April, the survey found, up 40,000 bbl/d from the previous month and short of the 254,000 bbl/d increase called for under the supply deal.

OPEC and its allies, known as OPEC+, are slowly relaxing 2020 output cuts as demand recovers from the pandemic. OPEC+ meets on May 5 and is expected to confirm a previously agreed output hike despite the surge in oil prices after Russia's invasion of Ukraine.

"Probably the view is to maintain the plan," an OPEC delegate said of the May 5 meeting.

The deal called for a 400,000 bbl/d increase in April from all OPEC+ members, of which about 254,000 bbl/d is shared by the 10 OPEC producers the agreement covers.

Output undershot the pledged hikes from October to March, with the exception of February, according to Reuters surveys, as many producers lack the capacity to pump more crude following insufficient investment, a trend accelerated by the pandemic.

As a result, the 10 OPEC members are pumping far less than called for under the deal. OPEC compliance with pledged cuts was 164%, the survey found, versus 151% in March.