Three Congolese republican guards were killed in an overnight attack at an airport at Lubumbashi, the country\'s second city, U.N. military spokesman said Wednesday. \"Unidentified gunmen attacked Luano airport in Lubumbashi. The toll is one republican guard who was burned to death and two others who died of gunshot wounds,\" Ibrahim Diene of the MONUSCO peacekeeping force said. \"The attackers managed to flee into the forest as other members of the republican guard fought back. An investigation is under way to determine the cause of what happened,\" he said. The attack took place late Tuesday. Lubumbashi lies on the southeastern tip of the Democratic Republic of Congo, 1,600 kilometers (1,000 miles) from the capital Kinshasa. The copper-mining town, a key economic hub in the region, is the Democratic Republic of Congo\'s second largest city. From DailyStar