Nigeria, Sept. 29 -- Nigeria's oil and gas industry was thrown into turmoil Monday as the Petroleum and Natural Gas Senior Staff Association of Nigeria (PENGASSAN) began a nationwide strike, shutting down key regulators and disrupting crude and gas supply.

The walkout, ordered by the union's National Executive Council, forced the Nigerian National Petroleum Company Limited (NNPCL), the Nigerian Upstream Petroleum Regulatory Commission (NUPRC) and the Nigerian Midstream and Downstream Petroleum Regulatory Authority (NMDPRA) to lock their offices. Workers across the country complied fully, union officials confirmed.

At NUPRC headquarters in Abuja, gates were padlocked with staff and visitors turned away. Similar shutdowns were reported at...