A state oil pipeline in Ecuador was hit by an act of "sabotage" on Wednesday, causing an oil spill into a river in the Amazon basin, the national company Petroecuador said.

The "sabotage" on the Trans-Ecuadorian Pipeline System (SOTE) caused a leak of crude that was "intentionally near a body of water" on the outskirts of Lago Agrio in the east, the company said in a statement, without specifying the amount of oil spilled or what the act of sabotage was.

Oil company workers placed containment barriers on the banks and across a river, according to photographs released by the firm on Twitter.

"New environmental disaster, the waters of the Conejo river contaminated by oil in the province of #Sucumbios," the Confederation of Indigenous Nationalities of the Ecuadorian Amazon said on Twitter.

A black and oily stain moved with the current of the river about 10 kilometers (six miles) from Lago Agrio, capital of Sucumbios, according to a video from the confederation.

The US NGO Amazon Frontlines, which advocates for the rights of indigenous peoples, also released a video on Twitter showing oil leaking from the pipeline at great pressure, contaminating land and water.

"Aerial images show the seriousness of the #oil spill of this #May 10 in the Conejo River - Lago Agrio - #Sucumb-os," it said on Twitter.