Kinshasa - Eighteen employees of a gorilla sanctuary in eastern Democratic Republic of Congo have been abducted by a militia group, sources said on Wednesday.An official with an NGO said the abduction took place on Monday in the area of Nzovu, which lies in the huge Kahuzi-Biega National Park, and an armed group called the Mai-Mai Raia Mutomboki was responsible.The victims comprise nine administrative employees, who were carrying out an inventory, and nine guards, the source said."(Eighteen) workers in the Kahuzi-Biega National Park were kidnapped by militiamen," Kashombana Bin-Saleh, administrator of Shabunda territory, confirmed to AFP."The 18 are alive and talks for negotiating their release will start as soon as a team from the (park) arrives in Shabunda," Kashombana added.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. The abductors are demanding a large ransom, according to sources in local civil society groups. They seized the group's luggage at the same time and forced local people to carry it. This group was released later, the sources said.The park extends over 6 000 square kilometres of rainforest - more than twice the size of Luxembourg - in largely mountainous terrain.The designated Unesco heritage site is one of the last refuges of the endangered eastern lowland gorilla, of which only about 250 now survive, as well as many other rare species.The park was established in 1970 by Belgian conservationist Adrien Deschryver, taking its name from two dormant volcanoes that lie within its boundaries.However, it abuts one of the most troubled regions in Africa, where armed conflicts have seethed for more than two decades.