Image copyright FREDERIC J. BROWN

A Canadian citizen who was detained in China amid frosty relations between the two countries has been released and returned to Canada, media reports say.

Teacher Sarah McIver, from Alberta, was held earlier this month for "unlawfully working in China".

Global Affairs Canada confirmed that a Canadian citizen had been released, but did not name the person.

Ms McIver's detention followed that of two other Canadians. They are still being held.

China and Canada both said Ms McIver's case was different from the other two. Former diplomat Michael Kovrig and businessman Michael Spavor face accusations of harming national security.

The detentions came amid a dispute between Canada and China following the arrest of Huawei chief financial officer Meng Wanzhou earlier this month. Ms Meng was held at the request of US prosecutors and faces extradition on charges of violating sanctions on Iran. She denies the allegations.

Image copyright AFP Image caption Canadians Michael Spavor (L) and Michael Kovrig are being accused of harming national security

China has denied the detention of the two men is tied to Ms Meng's arrest, but many analysts believe it is a tit-for-tat action.

Ms McIver had been working at a school in China when she was held over issues with her work visa.

"Global Affairs can confirm that a Canadian citizen, who was detained in China this month, has been released and has now returned to Canada," spokesman Richard Walker said.

"Due to the provisions under the Privacy Act, no further information can be disclosed."