Argentina's YPF was among the firms hit by the Saturday strike by contractors working in and around the oil fields the latest in a series of labor disputes to hit the Patagonian province of Chubut in the south of the country.
The protests have raised concerns about possible fuel shortages in Argentina as double-digit inflation stokes ever higher salary demands.
"There is no activity in any YPF oilfields in Chubut province," said a spokesman for YPF, the local unit of Spain's Repsol. "It is affecting our activities and those of other companies."
Officials at other energy companies with operations in the province, including producer Pan American Energy, could not immediately be reached for comment.
Trade union strikes are common at this time of year in Argentina, Latin America's No. 3 economy, but labor unrest has been particularly intense this season as workers negotiate contracts based on fast-rising consumer prices.
Annual inflation is running at about 25 percent in Argentina, according to private estimates.
In recent weeks, Argentina's energy industry has been plagued by a series of protests by refinery workers, oil field workers, truck drivers, security guards and teachers blocking access roads.