(Adds Banro Corp statement, stock lower)
KINSHASA, Feb 7 (Reuters) - Armed robbers attacked Banro Corp's Twangiza gold mine in eastern Democratic Republic of Congo early on Tuesday and three policemen and one assailant were killed, the Canadian company said.
A security guard was also injured when the group of men attempted to enter the gate at the mine site camp, the company said. One of the robbers is in police custody.
Police opened fire on the raiders, ending the assault, Banro's vice president for government relations, Désiré Sangara, earlier told Reuters.
No items were stolen and operations at the mine continue as normal, Banro said in a statement.
It said the attack, which was recorded by company surveillance cameras, was immediately reported to authorities and is being investigated.
Twangiza opened in 2011 and has become the most advanced of Banro's four gold mines in eastern Congo.
It has been plagued by illegal miners squatting on the site and by armed groups, some of the dozens of militias that remain active despite the official end to a regional conflict in 2003.
Shares in Banro listed on the Toronto Stock Exchange were 2.3 percent lower at 21.5 Canadian cents. (Reporting by Aaron Ross in Kinshasa; Additional reporting by Nicole Mordant in Vancouver; Writing by Emma Farge; Editing by Andrew Heavens and Grant McCool)