Kinshasa - Rebels attacked a United Nations peacekeeping base in eastern Democratic Republic of Congo, killing at least 14 peacekeepers and wounding 40 others in the worst violence against the mission in this Central African country in years.Deputy spokesperson Farhan Haq in New York said the peacekeepers were mainly from Tanzania, and that at least five Congolese soldiers also were killed in the assault blamed on one of the region's deadliest rebel groups."It's a very huge attack, certainly the worst in recent memory," Haq said.The peacekeeping base is located about 45km from the town of Beni, which has been repeatedly hit by rebels from the Allied Democratic Forces rebel group.The base is home to the peacekeeping mission's rapid intervention force, which has a rare mandate to go on the offensive, according to Radio Okapi, which is backed by the UN mission.The radio station, citing military sources, said fighting lasted four hours.Nearly 300 peacekeepers have been killed since the UN mission arrived in 1999, according to UN peacekeeping data.DRC, a country the size of Western Europe, has seen immeasurable cruelty and greed as a result of its vast mineral resources. The nation suffered through one of the most brutal colonial reigns ever known before undergoing decades of corrupt dictatorship. Back-to-back civil wars later drew in a number of neighbouring countries.The conflicts have been numerous since the UN mission's arrival. Many rebel groups have come and gone, at times invading the regional capital, Goma. One of the greatest threats in the region now comes from the ADF.The rebel movement has been active since the 1990s but intensified its attacks inside DRC several years ago. Human rights groups say at least 1 000 people have been killed in the last three years.While the group's members are mainly Muslim, experts say there are no proven links between the ADF rebels and other extremist organisations in Africa.The UN mission in 2006 helped carry out DRC's first free and fair elections in 46 years, but since then the winner of that vote, President Joseph Kabila, has become further entrenched in his post. Anger has grown as presidential elections originally set for late last year have been repeatedly delayed.