A Canadian teacher arrested in China for administrative reasons -- a case officially unrelated to the ongoing diplomatic row between Beijing and Ottawa -- has been freed, authorities said Friday.

Global Affairs Canada "confirms that a Canadian citizen, who was detained in China in December, was released and has now returned to Canada," spokesman Richard Walker said, without providing further details.

The arrest of Sarah McIver, a teacher accused of working illegally in China, was announced shortly after that of two other Canadian nationals: former diplomat Michael Kovrig, employed by think tank International Crisis Group, and Michael Spavor, a consultant on North Korea. 

The two men, whom China arrested on December 10, were detained on suspicion of "harm to national security" -- a phrase often used by Beijing when alleging espionage.

But many observers believe it was retaliation following the early December arrest in Vancouver of Chinese telecommunications giant Huawei's chief financial officer, Meng Wanzhou.

Ottawa has repeatedly said Meng's arrest was not political, but rather part of a judicial process in keeping with an extradition treaty with Washington. (AFP)