Venezuela’s state oil firm PDVSA said there had been an oil spill in the central Anzoategui state.
The incident is impacting on drinking water and has affected communities during an operation over a radius of 31 miles.
In a statement, PDVSA said the leak occurred in a 36-inch (91 cm) pipeline in the locality of Santa Clara.
PDVSA launched an operation to supply drinking water and protect local ecosystems, it added, giving no further details.
An opposition lawmaker from Anzoategui, Jose Brito, said the leak occurred between Wednesday and Sunday and that 25,000 barrels had spilled, causing an “ecological disaster.”
Blaming poor maintenance for the spill and saying security forces were blocking access to the area, Brito urged the opposition-led legislature to open an investigation.