Canadian police warned in a leaked document Wednesday of growing threats to the country's oil industry by militant climate activists opposed to the use of fossil fuels.

Greenpeace called the year-old report obtained by AFP "chilling," because of its broad-brush depiction of climate-change activists as potential extremists.

In the report, the Royal Canadian Mounted Police describes "a growing, highly organized and well-financed, anti-Canadian petroleum movement" that is largely peaceful but includes "militants and violent extremists who are opposed to society's reliance on fossil fuels."

It said this ideologically motivated fringe group is willing to go beyond peaceful actions, and use vandalism and sabotage, or advocate the use of arson, firearms and bombs to force a stoppage in activities that contribute to global warming.

In some cases, the RCMP said they have aligned themselves with "violent aboriginal extremists" while attracting hundreds of millions in funding from foundations and wealthy individuals in the United States.

It commented that "the arrival of outside influence, financial support, and direction can inflame an already tense environment."

The document cites as examples clashes between protesters and police in New Brunswick in October 2014 that saw six RCMP vehicles burned and 40 people arrested, as well as weapons and explosives seized.

Between 2006 and 2013, there was also the bombing of an oil executive's car and another's home, threats against the shale gas industry, and attacks on infrastructure including pipelines.

The RCMP was not immediately available to comment.

But RCMP spokesman Sergeant Greg Cox told local media that federal police do not conduct surveillance unless there is suspicion of criminal conduct.

Greenpeace's Keith Stewart, however, said: "The big problem is that this document classifies anyone who is concerned about climate change as a potential (if not actual -- the lines are very blurry) 'anti-petroleum extremist' looking to advance their 'anti-petroleum ideology.'"

The RCMP said militants are currently focused on New Brunswick and British Columbia provinces, where new shale gas and pipeline projects are underway, respectively.

But it added that "as the petroleum industry expands its operations across Canada, criminal activity associated to the anti-petroleum movement will increase nationally."