This mineral wealth has been plundered by foreign groups since the colonial era and is one of the main reasons why the region has been plagued by instability for the last 30 years.

Militia groups control many of the mines in eastern DR Congo and their leaders become wealthy by selling it to middle-men.

Purusi said some of these dealers in precious metals enjoyed good relations with influential people in the capital, Kinshasa, and this was why the mission to carry out these latest arrests had to be kept quiet.

He said they had been acting on a tip-off and that the gold and money was only found after a meticulous search of the vehicle in the Walungu area not far from the border with Rwanda.

He did not say exactly how much gold had been seized.

Last month, the governor told reporters he was shocked to hear that 17 Chinese nationals, who had been arrested on allegations they had been running an illegal gold mine, had been freed and allowed to return to China.

He said this undermined efforts to clean up DR Congo's notoriously murky mineral sector.

They owed $10m in taxes and fines to the government, the Reuters news agency quotes him as saying.

The Chinese embassy has not commented on the allegations.

The arrests come as fighting continues to flare in the neighbouring North Kivu province, where a Rwanda-backed rebel group has captured large areas of territory.

Last month, DR Congo said it was suing Apple over the use of "blood minerals", prompting the tech giant to say it had stopped getting supplies from both DR Congo and neighbouring Rwanda.

Rwanda has denied being a conduit for the export of illegal minerals from DR Congo.

In their lawsuit, lawyers acting for the Congolese government alleged that the minerals taken from conflict areas was then "laundered through international supply chains".

"These activities have fuelled a cycle of violence and conflict by financing militias and terrorist groups and have contributed to forced child labour and environmental devastation," they said.