Ecuadorean plaintiffs filed a lawsuit in Canada as a first move outside their country to try and enforce an $18 billion court judgment against oil company Chevron for polluting the Amazon, their lawyers said on Wednesday.

The 2011 judgment against Chevron is one of the biggest rulings ever for environmental damage and is being tracked closely by the global oil industry.

Issued by an Ecuadorean court in the jungle region at the heart of the dispute, the ruling was upheld by an appeals court in January - but Chevron has appealed to Ecuador's Supreme Court.

Since U.S.-based Chevron no longer has assets in Ecuador, the plaintiffs are trying to get the ruling enforced outside the OPEC-member country.

The new lawsuit, filed in the Superior Court of Justice in Ontario, targets Chevron and various subsidiaries that together hold significant assets in Canada, the plaintiffs' legal team said in a statement.

"While Chevron might think it can ignore court orders in Ecuador, it will be impossible to ignore a court order in Canada where a court may seize the company's assets if necessary to secure payment," said Pablo Fajardo, the lead lawyer for the plaintiffs.