Beijing has already detained two Canadians for allegedly harming national security, a move perceived to be in response to the arrest of Chinese telecom giant Huawei's Chief Financial Officer Meng Wanzhou in Canada.
A report in the Global Affairs Canada said the Canadian Foreign Ministry was "aware of a Canadian citizen" who had been detained in China. The ministry, however, did not explain if the third detention was linked to Meng's arrest.
In response, the Chinese Foreign Ministry said it was not aware of any arrest. "I have not heard of it," said ministry's spokesperson Hua Chunying.
While Kovrig worked for International Crisis Group, Spavor organised tours in North Korea.
Though Meng has been granted bail, she faces possible extradition to the US for allegedly doing business with Iran in violation of US sanctions.
(With inputs from agencies.)