image copyrightToronto Star via Getty Imagesimage captionCanadian firefighters (File photo)

Two more Catholic churches burned down in indigenous communities in western Canada early on Saturday.

The fires at St Ann's Church and the Chopaka Church began within in an hour of each other in British Columbia.

Officers said both buildings were completely destroyed, and that they are treating the fires as "suspicious".

Last Monday two other Catholic churches in the province were destroyed in fires, as Canada marked National Indigenous People's Day.

"The investigations into the previous fires and these two new fires are ongoing with no arrests or charges," RCMP Sgt Jason Bayda said.

It comes as hundreds of unmarked graves have been discovered at sites of former residential schools in Canada.

The government-funded compulsory schools were run by religious groups in the 19th and 20th centuries with the aim of assimilating indigenous youth.

Indigenous groups have demanded a nationwide search for more graves.

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Lower Similkameen Indian Band Chief Keith Crow told public broadcaster CBC that he was received a call early in the morning saying that the Chopaka Church was on fire. It had burned to the ground by the time he arrived half-an-hour later.

"I'm angry," the chief told CBC. "I don't see any positive coming from this and it's going to be tough."

He said many in the community are Catholic church members and were very upset about the blaze.

In May, the Tk'emlups te Secwepemc First Nation announced the discovery of a mass grave at a school in British Columbia.

They found the remains of 215 children at the Kamloops Indian Residential School, which was opened under Roman Catholic administration in 1890 and closed in 1978.

And on Thursday, the Cowessess First Nation said it had found 751 unmarked graves at a former residential school in Saskatchewan. The Marieval Indian Residential School was also operated by the Roman Catholic Church.

Between 1863 and 1998, more than 150,000 indigenous children were taken from their families and placed in these schools throughout Canada.

A commission launched in 2008 to document the impacts of this system found that large numbers of indigenous children never returned to their home communities. The commission's landmark report said the practice amounted to cultural genocide.

The Canadian government has formally apologised for the system.

media caption"No reconciliation without truth": A survivor recounts abuse in Canadian residential school