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.

"We plan to exercise our legal right to collect every penny of the legitimate judgment from Ecuador, even if we have to drag Chevron kicking and screaming into courts around the world."

The plaintiffs accused Texaco, which was later taken over by Chevron, of causing illnesses among the local population by dumping drilling waste in unlined pits in the 1970s and 1980s.

Chevron denies the accusations. It says Texaco did not pollute the jungle, and that it properly cleaned up all the pits for which it was responsible.

"The Ecuador judgment is a product of bribery, fraud, and it is illegitimate. The company does not believe that the Ecuador judgment is enforceable in any court that observes the rule of law," the company said in a statement on Wednesday.

The legal saga has spanned nearly two decades and is under scrutiny for precedents that could impact other claims against multinationals accused of pollution elsewhere around the world.

The case has also become a cause celebre for environmental activists who cast the decision in favor of the plaintiffs as victory of David vs. Goliath proportions.

Filled with intrigue, accusations of corruption, bribery and dirty tricks, the complicated case is now being fought on multiple fronts including Ecuador's Supreme Court, a New York court handling a racketeering lawsuit filed by the company, and an international arbitration tribunal.     

(By Eduardo Garcia, with editing by Andrew Cawthorne and Eric Beech, Reuters, 30/05/2012)