BEIJING/LUSAKA (Reuters) - Zambia has detained 31 Chinese nationals for illegal mining in the African country’s copper belt but has failed to provide strong proof of their crimes, a senior Chinese diplomat said as he lodged a complaint.

Lin Songtian, the Chinese Foreign Ministry’s director-general for African affairs, told a Zambian diplomat in Beijing that China understood and supported actions to crack down on illegal mining, the ministry said in a statement late on Sunday.

However, Zambia had not only not provided strong proof of the crimes of the 31 detained but had also detained a pregnant woman and two victims of malaria, Lin said.

“China expresses serious concern and resolute opposition to this,” the ministry cited Lin as saying.

Zambia’s Home Affairs Minister Stepehen Kampyongo said he held a meeting with Chinese Embassy officials on Monday over the matter but declined to give further details, saying Zambia’s immigration department was handling the matter.

Immigration department chief Moolo Milimo told the Times of Zambia that the 31 Chinese, who were arrested in the copperbelt town of Chingola, would be deported, according to the newspaper’s online edition.

“We have taken the position that the 31 Chinese who were arrested in Chingola on Saturday have to be deported to their country for failure to conform to the laws of the country (Zambia),” Milimo said.

China hoped Zambia could handle the incident appropriately and as soon as possible, and release the innocent, Lin said.

The government has always asked Chinese companies and citizens to respect the laws of the countries where they operate, Foreign Ministry spokeswoman Hua Chunying said on Monday.

China, however, opposes “selective” law-enforcement actions against its citizens, she told a daily news briefing.

“China will continue to pay close attention to developments in this case,” she added.

Chinese companies have invested more than $1 billion in copper-rich Zambia but there has been animosity, with some Zambian workers accusing firms of abuses and underpaying.

In 2012, Zambian miners killed a Chinese supervisor and seriously wounded another in a pay dispute at a coal mine.

Zambian police charged two Chinese supervisors at the same coal mine with attempted murder two years earlier, after the shooting of 13 miners in a pay dispute.

Resource-hungry China is investing heavily in Africa, a supplier of oil and raw materials such as copper and uranium, but critics have warned its companies take with them their poor track record on workers’ rights and environmental protection.