Zimbabwe has accused the US of mischief in blocking rough diamond imports from the Marange fields over concerns of forced labour.

In a notice on Tuesday the US Customs and Border Protection banned targeted products from Zimbabwe, China and the Democratic Republic of Congo

The choice of countries has sparked suspicions of the blockade being an extension of Washington DC's trade war with China.

The US said the embargo followed concerns that treasured stones were produced with forced labour, a withhold release order that baffled Harare.

“To even suggest that Zimbabwe has some form of corporate forced labour is mischievous or simply ignorant,” said Nick Mangwana, a government spokesman.

Zimbabwe's constitution prohibits forced, compulsory labour or slavery in any form, he said.

“As government, we have a very strong revulsion towards any form of slavery or servitude," Mr Mangwana said.

He said the government would engage the US on the matter, describing it as "a manifestation of undeclared sanctions that have hurt the economy."

Diamond mining in the Marange area in eastern Zimbabwe has long been a source of controversy with allegations of human rights violations.

In 2016, then Zimbabwean president Robert Mugabe said diamonds from Marange worth $15 billion could not be accounted for.

The government said it would nationalise the diamond mines but President Emmerson Mnangagwa, who took over from the late Mugabe, has rolled back the plans.

A Chinese company, Anjin, is one of the prominent miners in Marange under a joint venture with the Zimbabwean military.

Its mines were nationalised in 2016 but it was allowed back under President Mnangagwa’s government.