This strike is the fourth one staged by the Nigerian Labor Congress (NLC) and the Trade Union Congress (TUC), two of the country's biggest unions, since President Bola Tinubu took office last year, Reuters reported.
The Transmission Company of Nigeria (TCN) said union members drove away operators at the country's power control rooms and shut down at least six substations, which eventually shut the national grid at 02:19 am (0119 GMT).
Nigerian airline Ibom Air said it was suspending flights until further notice due to the strike, while another, United Nigeria, said airports across the country have been shut down and that striking workers had permitted none of its flights to operate.
Since taking office, Tinubu has embarked on Nigeria's boldest reforms, which has fueled a rise in inflation to an almost 30-year high and worsened a cost-of-living crisis in Africa's most populous nation.
Unions declared an indefinite strike on Friday after talks for a new minimum wage meant to cushion the impact of reforms collapsed. They said the strike would last until a new minimum wage was in place.