Amnesty International on Thursday said two major oil companies operating in Nigeria, Shell and ENI, reported a combined 553 oil spills in 2014, a "seriously alarming" figure that qualifies as a "national emergency."
The rights watchdog said that analysis of the latest figures released by both companies established that Anglo-Dutch Shell reported 204 spills last year, while the Italian major ENI admitted 349.
"These figures are seriously alarming. ENI has clearly lost control over its operations in the Niger Delta," the southern, crude producing region, said Audrey Gaughran, Amnesty's Global Issues Director.
"And despite all its promises, Shell has made no progress on tackling oil spills," she added.
Amnesty said that, by contrast, only 10 spills were reported across all of Europe between 1971 and 2011.
"In any other country," Nigeria's spill figures "would be a national emergency," Gaughran said. "In Nigeria it appears to be standard operating procedure for the oil industry."
Amnesty also questioned the credibility of the figures provided by the companies concerning the total amount of oil spilled as a result of the 553 incidents.
The 30,000 barrels, or five million litres, reported is "highly likely to be a significant underestimate," the group said, citing poor reporting of spills in the Niger Delta.
The delta has been devastated by oil-related pollution for decades, creating resentment among a local population which has also largely missed out on the benefits of Nigeria's vast energy wealth because of corruption.
Shell has long insisted that most spills are the result of pipeline vandalism by local gangs which syphon off crude for sale on the black market.
Amnesty has however challenged such claims, repeatedly calling on Shell and foreign companies to invest in needed infrastructure repairs.
Nigeria, Africa's top crude oil producer, will hold national elections on March 28.
The incumbent President Goodluck Jonathan is a native of the Niger Delta, but critics say he has not done enough to clean up corruption in the industry or steer crude revenue to the region's people.
Explore further: No action from Shell, Nigeria on oil pollution report: Amnesty