Nigeria began drilling for oil and gas in the northeast on Tuesday, a first for the African oil giant, which has exploited large deposits in the south for decades and whose production is declining.

President Muhammadu Buhari visited the Kolmani field, located in Gombe and Bauchi states and with estimated reserves of over 1 billion barrels of crude, to inaugurate the drilling site.

"The successful discovery of the Kolmani Oil and Gas field by NNPC [Nigerian National Petroleum Company Limited] and her partners has finally broken the jinx" after long efforts to find commercial oil and gas outside the established Niger Delta Basin, Buhari said in a statement.

In addition to drilling, the project — which has attracted $3 billion in investment — aims to open an oil refinery, a gas processing unit, a power plant and a fertilizer factory, according to the presidential statement.

Buhari in his comments also urged the oil company and partners "to ensure all lessons learnt from our years of experience as an oil-producing nation are utilized to ensure harmonious relationship with the local communities."

Oil exploitation in Nigeria began in the 1960s in the southeastern Niger Delta region.

Decades of production have enriched government officials and generated huge profits for large foreign companies in particular, but the majority of Nigerians, especially in the oil-rich Delta region, continue to live in poverty.

The region suffers badly from pollution, and tens of thousands of people now make a living from stealing crude oil from pipelines or at sea, from illegal refineries that have sprung up in swampy and forested areas, and from selling fuel on the black market, causing ecological disasters.

This insecurity in the sector has significantly increased the cost of producing Nigerian oil, and major foreign oil companies are now ceding their share of onshore oil fields to focus on offshore operations.

In September, Nigeria lost its position as the largest oil producer on the African continent to Angola as its oil production continued to decline despite rising prices linked to the Russian offensive in Ukraine.

In addition to a severe economic crisis, Africa's most populous country also faces widespread insecurity, with attacks by criminal groups and a jihadist insurgency in the north, and separatist unrest in the southeast.

In the face of these problems, Nigerian voters will go to the polls in February to elect a successor to Buhari, who is stepping down after two terms.

On Tuesday, Buhari also reiterated Nigeria's goal to achieve net zero carbon emissions by 2060.