(Recasts with reports from Bangui, rebel spokesmen, background) By Paul-Marin Ngoupana BOSSANGOA, Central African Republic, Nov 12 (Reuters) - Rebels in northern Central African Republic killed more than a dozen soldiers in an ambush near the Chadian border, government officials said on Wednesday. Various rebel groups operating across the north of the impoverished, landlocked country have become more active as the government has pressed ahead with plans for a national dialogue in December aimed at ending years of instability and bloodshed. General Gabriel Baipo, prefect of the Ouham district, told Reuters in the cotton trading town of Bossangoa that rebels had killed 14 soldiers late on Tuesday further north near the locality of Sido, close to the border with Chad. Baipo blamed the Popular Army for the Restoration of the Republic and Democracy (APRD), one of several rebel groups waging low-level campaigns against President Francois Bozize. But an Interior Ministry statement broadcast on state radio accused the Democratic Front for the Central African People (FDPC) of Abdoulaye Miskine, a former associate of former President Ange-Felix Patasse, who was overthrown in a 2003 coup. The Ministry statement gave no death toll. Media reports from the capital Bangui quoted family members of the victims as saying 13 soldiers had been killed. The attack happened in a volatile border region where human rights groups say local villagers have suffered repeated raids, killings and looting by rebels, bandits and government troops. Many rural communities have set up home in fields they cultivate well away from major roads, only returning to their empty villages to fetch water from those hand-pumps still working, carrying it back on their heads through the arid scrub. The thinly-populated nation, which has a history of coups and revolts, has deposits of diamonds, and reserves of uranium, which a French company is due to start mining in 2010. CEASEFIRE UNRAVELS Spokesmen for both Miskine and APRD leader Jean-Jacques Demafouth in Bangui said they had no details on the ambush save for those broadcast on state radio, and could not say for sure who had carried it out. The attack occurred as envoys sent by President Bozize were travelling in the north of the country to tell local people about the faltering government initiative to make peace with the rebel groups which signed a broad ceasefire accord in June. Justice Minister Thierry Maleyombo cancelled plans to visit villages north of Bossangoa after local APRD fighters warned him he would face attack, government officials said. The ceasefire between the government and rebels has begun to unravel since early August, when rebel and opposition envoys walked out of talks on an amnesty for insurgents. Bozize promulgated the amnesty despite objections to its scope from both rebel leaders and political opponents. He has called for all-inclusive political negotiations in December. But rebels have stepped up operations across the north. European Union peacekeepers deployed near the volatile Sudan border in the northeast of the country, where the Union of Democratic Forces for Unity (UFDR) rebel group operates, said armed men attacked an army post in the town of Ouandja early on Saturday. But government troops regained control within hours. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/) (Additional reporting by Alistair Thomson in Dakar; Writing by Pascal Fletcher and Alistair Thomson)