Kuwaiti oil and gas industry workers began a strike on Sunday over public sector pay reforms which they fear could reduce salaries and diminish other benefits, union members said.
Non-Kuwaiti workers in the industry did not go on strike, however, and it was not immediately clear if oil and gas output was seriously affected.
Kuwait National Petroleum Co (KNPC), a subsidiary of Kuwait Petroleum Corp (KPC) and one of five state-owned companies affected, has said there is a contingency strategy to ensure production and exports will not be hurt.
The union has not said how long the strike, involving thousands of workers at state-owned oil, gas and petrochemical companies, will last.
KPC and its subsidiaries agreed to temporarily freeze a planned government overhaul of the payroll system and seek a compromise through a joint committee with the workers' union, a spokesman for Kuwait's oil sector, Sheikh Talal al-Khaled al-Sabah, said last week.
But the union head, Saif al-Qahtani, called that "playing with words". "The KPC statement is talking about 'freezing' the decisions, while our demand is to cancel them," Qahtani, head of the Oil and Petrochemical Industries Workers Confederation, told Reuters.