China's Foreign Ministry has said that a Canadian woman is undergoing "administrative punishment" for working illegally, after Canada's Government said a third Canadian had been detained in China.

Key points: Beijing has identified the third Canadian to be detained in China as Sarah McIver

Beijing has identified the third Canadian to be detained in China as Sarah McIver Canadian media report she is an English teach being held over "visa complications"

Canadian media report she is an English teach being held over "visa complications" Both China and Canada say her case is unrelated to the two other detentions

Chinese state security agents last week detained two Canadians, former diplomat Michael Kovrig and businessman Michael Spavor, saying they were suspected of endangering state security.

The two Canadians were detained after the December 1 arrest in Vancouver of Meng Wanzhou, chief financial officer of the Chinese telecommunications giant Huawei.

Ms Meng was arrested at the request of the United States, which is engaged in a trade war with China.

Chinese Foreign Ministry spokeswoman Hua Chunying identified the third Canadian as Sarah McIver, who was serving "administrative punishment" due to "illegal employment". She did not elaborate.

"What I can tell you is that China and Canada are maintaining clear consular communication," Ms Hua told a daily news briefing.

When asked if Ms McIver's case was connected to Mr Kovrig and Mr Spavor, Ms Hua pointed out the nature of the cases were different, given the other two were accused of endangering national security.

Former diplomat Michael Kovrig (L) and businessman Michael Spavor (R) have been detained in China. ( AP )

Ms Hua referred further questions on Ms McIver to the Ministry of Public Security. That ministry did not immediately respond to requests for further comment.

The Canadian Government has not identified the third Canadian, though Canadian media has said the person is Ms McIver, an English teacher who is being held because of "visa complications".

Canadian Prime Minister Justin Trudeau urged caution and said he would not be "stomping on a table" after China detained the third Canadian.

Mr Trudeau said he was asking China for more information on the detentions but said the latest incident was "a very separate case" from the other two.

The Canadian Government has said several times it saw no explicit link between the arrest of Ms Meng, the daughter of Huawei's founder, and the detentions of Mr Kovrig and Mr Spavor.

But Beijing-based Western diplomats and former Canadian diplomats have said they believed the detentions were a "tit-for-tat" reprisal by China.

China has demanded Ms Meng's immediate release and summoned the Canadian and US ambassadors to complain about the case.

The US accuses Ms Meng of misleading multinational banks about Iran-linked transactions, putting the banks at risk of violating US sanctions.

She was released on bail in Vancouver, where she owns two homes, while waiting to learn if she will be extradited to the US. She is due to appear in court on February 6.

Reuters