(Removes old oil union quote)
* Talks between government, unions break down
* Oil union says it will join stoppage
* Evidence shows patchy adherence to strike
* NNPC says no sign oil output affected
By Chijioke Ohuocha and Camillus Eboh
LAGOS/ABUJA, Sept 27 (Reuters) - Nigeria's main unions launched an indefinite strike on Thursday in a dispute over the minimum wage and a key oil industry union said it would join, in a decision that could potentially impact crude output.
The strike began a day after talks between President Muhammadu Buhari's government and unions broke down. It is intended to raise pressure on authorities to produce a minimum wage proposal.
Unions want the monthly minimum wage raised to about 50,000 naira ($164) from 18,000 naira.
Buhari had vowed to review the wage due to a fuel price hike and currency devaluation in the last two years aimed at countering the effects of a global oil price plunge that hit the country hard, given its status as Africa's biggest crude producer.
Buhari plans to stand for a second term at an election next February and his economic record will come under scrutiny, given previous pledges to raise living standards, tackle corruption and improve security.
Evidence suggested patchy adherence to the strike. Government offices were shut in the capital, Abuja, while most of the city's banks were closed, but witnesses said the commercial capital Lagos was largely unaffected.
Schools in Maiduguri, capital of northeastern Borno state, were closed.
"I am in total support of the strike because almost all commodities have increased - food stuffs, rent is very high. Basically all necessities have doubled in price," said civil servant Stan James.
The possible impact of the strike on oil is important because it is a mainstay in Nigeria, a country with the biggest economy in Africa.
Oil union PENGASSAN said: "We are to proceed on the action with immediate effect. However, those on critical and essential services are required to remain on their duty posts."
But a spokesman for Nigerian National Petroleum Corporation said he had seen no sign the strike was affecting production, while Cogent Ojobor, a leader in the Niger Delta region for the Nigeria Union of Petroleum and Natural Gas Workers, said: "No oil company is affected for now."
South African telecoms company MTN told staff to work from home due to the strike.
Last year Nigeria emerged from its first recession in a quarter of a century. Growth remains fragile and consumer spending is yet to recover. Analysts said a prolonged strike could tip the country back into recession.
Nigeria's accountant general urged workers to call off the strike, saying the government was looking into their grievances. (Additional reporting by Camillus Eboh in Abuja, Ola Lanre in Maiduguri, Tife Owolabi in Yenagoa and Chijioke Ohuocha in Lagos, Writing by Matthew Mpoke Bigg, Editing by William Maclean)