LAGOS, Aug 10 (Reuters) - The Dangote Oil Refinery has

called on Nigeria's upstream oil regulator to force producers to

abide by a law that stipulates they supply local refineries,

saying that lax enforcement was raising its operational costs.

The 650,000-barrel-per-day capacity refinery, built by

Africa's richest man Aliko Dangote on the outskirts of Lagos for

$20 billion, has struggled to get sufficient supplies from

Nigeria, where vandalism and low investment impede oil

production.

In a statement issued on Friday, Dangote Refinery accused

the Nigerian Upstream Petroleum Regulatory Commission (NUPRC) of

failing to enforce the Domestic Crude Supply Obligation (DCSO),

a provision that requires crude oil producers to supply domestic

refiners with a portion of their production.

"Our concern has always been that the NUPRC is pushing, but

the international oil companies are not following the

instructions," said Anthony Chiejina, a Dangote Refinery

spokesperson in the statement.

"Consequently, we often purchase the same Nigerian crude

from international traders at an additional $3-$4 premium per

barrel which translates to $3-$4 million per cargo," he said.

The refinery said it was expecting to receive 15 cargoes for

September out of which NNPC had allocated them six.

In a statement, the NUPRC said some producers were

experiencing operational challenges while others had pledged

most of their output to oil traders who financed drilling. It

also said forcing them to raise their supply would violate their

contracts.

Dangote Refinery requires 325,000 bpd of supply, but since

it started operating in January, it has received nearly half of

that amount, data from the regulator shows.

The DCSO was created by Nigeria's 2021 Petroleum Industry

Act, but it has proven difficult to enforce due to dwindling oil

production and the cash-strapped state-owned Nigerian National

Petroleum Corporation using much of its production for

crude-backed loans.

The Dangote Oil Refinery has also had a row with the

downstream regulator over fuel imports, as it scrambles to

compete in a challenging environment.