Rescue workers struggled on Monday to reach the wreckage of a U.N. helicopter that crashed in the forests of eastern Congo with four Russian crew members on board, a U.N. spokesman said.
The helicopter crashed on Saturday on a thickly wooded mountainside around 30 km (18 miles) west of Bukavu airport, spokesman Biliaminou Alao told Reuters.
"The area is difficult to access, they're going to have to climb the mountain to get to the crash site," he said, adding that around 40 rescuers were trekking to there on foot, accompanied by Congolese military.
"We've heard nothing from the crew, there's no communications network in that area ... but I remain hopeful."
Russia's Foreign Ministry was less optimistic about the fate of the crew after the crash that it blamed on adverse weather conditions.
"The fate of the Russian crew ... remains unclear for now but, given the circumstances of the crash, some experts assess they had no real chance of surviving," its statement said.
U.N. spokesman Martin Nesirky said the United Nations was in close contact with Russia, which provided the helicopter for the peacekeeping mission. Russia's Foreign Ministry said it was an Mi-8 helicopter owned by UTair.
The United Nations has an estimated 17,000 peacekeepers in Congo, and operates an extensive aviation network to counter an almost total lack of roads in the vast central African country.
The peacekeepers have been stretched thin by a rebellion in the resource-rich east of Congo and the U.N. Security Council is considering creating a special intervention force, which one senior council diplomat has said would be able to "search and destroy" the M23 rebels and other armed groups in the country.
Air accidents are common in the country and in 2011 a U.N. passenger plane crashed in the capital Kinshasa, killing all but one of the 33 people on board.
At least five people were killed when a twin-propeller plane crashed last week as it tried to land in bad weather in the town of Goma, north of Bukavu.