Thirty-one Chinese nationals, held for illegal mining in Zambia, have been deported.

China said Zambia had provided insufficient evidence to justify the arrests.

It said one of those detained in the copper mining town of Chingola was a pregnant woman.

Zambian media said the Chinese were using children to steal copper from the mines.

There has been animosity between the Chinese and local communities in recent years, with Zambians complaining of abusive treatment and low pay.

China has invested more than $1bn (£980m) in Zambia, mainly in copper mines.