U.N. officials say a group of Congolese soldiers conducting a massive joint operation with U.N. peacekeepers mutinied Wednesday in the lawless east, forcing a halt to the mission. The mutineers then returned to a U.N. base where they threatened their superiors, began looting and are believed to have shot at a U.N. helicopter on Thursday.

Congo's new national army is supposed to draw from the tens of thousands of gunmen who fought in various factions during the country's five-year war.

The force remains chaotic, untrained, and poorly paid. But in an attempt to improve the army and pacify the lawless east, U.N. peacekeepers are providing food, water and transport as the forces conduct joint operations.

But a mutiny by a group of government soldiers, who fled the front line and returned to their bases mid-battle, underlines the fragility of the military just months before historic elections are due to be held.

U.N. officials say the troops, who had been fighting alongside the peacekeepers, threatened their superiors at their headquarters and looted part of the U.N. base they were operating from.

The situation later appeared to have calmed down but when U.N. and Congolese generals tried to land by helicopter at the base in Ituri, in Congo's wild northeast, the aircraft apparently came under fire by the mutineers. 

A U.N. spokesman later said it could not be confirmed the mutineers were responsible. But the joint operation against militia fighters has been suspended until discipline is restored to the ranks of the Congolese fighters.

Numerous armed groups continue to operate in Congo's lawless east, where the war officially ended three years ago.

The fighters make vast tracts of the mineral rich land ungovernable and too dangerous for aid workers to access, leaving hundreds of thousands without access to the most basic healthcare.

Congo's last war is believed to have killed four million people, mostly from hunger and disease, leading many to dub it the worst humanitarian crisis since the World War II.