Three Chinese nationals have been arrested with 12 gold bars and $800,000 (£650,000) in cash in eastern Democratic Republic of Congo, officials say.

The gold and money were hidden under the seats of the vehicle they were travelling in, according to Jean Jacques Purusi, the governor of South Kivu province.

He said the operation to arrest the men had been kept secret after the recent release of another group of Chinese nationals accused of running an illegal gold mine in the area.

Eastern DR Congo has abundant reserves of gold, diamonds, and minerals that are used to make batteries for mobile phones and electric vehicles.

Foreign groups have plundered this mineral wealth since the colonial era, which is one of the main reasons 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 middlemen.

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 were 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.