Suspected militiamen have kidnapped five workers at Banro Corp's Namoya gold mine in eastern Democratic Republic of Congo, the company said on Thursday, in the second attack on its facilities in a month.

The attack took place during the night of Tuesday into Wednesday and an investigation is underway, Crispin Mutwedu, a senior Banro official, told Reuters, adding that a local militia had been threatening the mine recently.

The hostages included a French national, a Tanzanian and three Congolese, he said. New York and Toronto-listed Banro's four gold mines in eastern Congo have been plagued both by illegal miners squatting on site and by armed groups - some of the dozens of militias that remain active despite the official end to a regional conflict in 2003.

Three police officers and one assailant were killed last month when armed robbers attacked Banro's Twangiza gold mine in neighboring South Kivu province. Namoya poured its first gold last January and produced93,253 ounces of gold in 2016.