Four Canadians were executed in China on drug-related charges earlier this year, Canadian authorities have confirmed.

Axar.az reports, citing BBC, all of them were dual citizens and their identities have been withheld, Canada's foreign minister Mélanie Joly said.

A spokesperson for the Chinese embassy in Canada reportedly urged Ottawa to "stop making irresponsible remarks", as pundits feared a further downturn in relations between the countries after years of strain.

China's foreign ministry said on Thursday that it had acted "in accordance with the law", while the embassy said there was "solid and sufficient" evidence for their crimes.

Beijing had "fully guaranteed the rights and interests of the Canadian nationals concerned", the embassy said, urging Canada to respect "China's judicial sovereignty".

China does not recognise dual citizenship and takes a tough stance on drug crimes. However, it's rare for the death penalty to be carried out on foreigners.

Joly said she had been following the cases "very closely" for months and had tried with other officials, including former prime minister Justin Trudeau, to stop the executions.

In a statement to Canadian media, Global Affairs Canada spokesperson Charlotte MacLeod said Canada had "repeatedly called for clemency for these individuals at the senior-most levels and remains steadfast in its opposition to the use of the death penalty in all cases, everywhere".

China imposes the death penalty on serious crimes including those related to drugs, corruption and espionage. While the number of executions are kept secret, human rights groups believe China has one of the highest execution rates in the world.