One of Nigeria's main oil and gas unions will join a nationwide strike starting on Oct. 3 to protest against government policies that are causing economic hardship for Nigerians, union leaders said on Thursday.

Nigeria is Africa's largest oil producer and relies on the commodity for around 90% of foreign exchange earnings and about half its budget.

Nigeria Union of Petroleum and Natural Gas Workers (NUPENG) directed its members to ensure "unwavering compliance" with the indefinite strikecalled by Nigeria's two biggest workers union federations.

NUPENG represents a myriad of workers across the entire value chain in the oil and gas sectors, including upstream oil platform workers, fuel tanker drivers and pump attendants, and its decision to join the strike is a significant escalation of the unions' dispute with the government.

NUPENG President Williams Akporeha said the government's policies have caused "excruciating and debilitating socio-economic pains" for Nigerians without any accompanying measures to cushion "the immediate effects and impacts."

President Bola Tinubu has been under pressure to reverse his decision to scrap a popular petrol subsidy that had kept fuel prices low but was costly on government finances.

While his policies have cheered investors, unions say they have led to soaring costs for Nigerians - an estimated four in 10 of whom live below the national poverty line- as they grapple with the highest inflation in nearly two decades.