A joint military operation by UN and Congolese troops to rout rebel forces from their strongholds in the Ebola-hit northeast Democratic Republic of Congo has "achieved quite significant results" and is still under way, the UN peacekeeping chief said on Friday.Jean-Pierre Lacroix clarified at a news conference that seven UN peacekeepers - six from Malawi and one Tanzanian - were killed in attacks and exchanges of fire on Wednesday with Allied Democratic Forces rebels along with 12 Congolese soldiers. The Security Council said late on Thursday that eight peacekeepers were killed.Lacroix said the UN and Congolese troops faced two separate attacks by ADF fighters near the regional capital, Beni, which is the largest city affected by the current Ebola outbreak and the centre of efforts to fight it."They returned fire. They repelled the first attack successfully," he said. "But then the armed group reorganised and in the second attack, unfortunately our peacekeepers appear to have been killed and injured."Lacroix said UN and Congolese forces captured an ADF base that was used to attack and threaten Beni.The UN envoy for DRC, Leila Zerrougui, said six ADF combatants were arrested.She said the UN and the Congolese army decided to launch the operation near Beni, where ADF and Mai-Mai rebel groups are especially active, to secure the area to allow medical and humanitarian teams to fight the Ebola outbreak. Attacks against military forces and civilians are complicating the response by health officials who are also meeting community resistance.DRC's health ministry said last week that the Ebola outbreak is the worst in the country's recorded history with 319 confirmed and probable cases. There have been about 200 deaths since the outbreak was declared August 1 in the volatile east.Eastern DRC, a mineral rich region, is home to many armed groups vying for control.Health Minister Dr Oly Ilunga Kalenga said last week that "no other epidemic in the world has been as complex as the one we are currently experiencing."He said response teams "have faced threats, physical assaults, repeated destruction of their equipment, and kidnapping" and two members lost their lives in an attack.The ADF originated in Uganda as a rebel movement against that country's government and carried out deadly bombings in the 1990s. A military campaign there forced them to relocate to eastern DRC.Zerrougui estimated the ADF had about 500 fighters who have integrated in the area, married Congolese and engaged in illegal mining."They consider this is their land and it was given to them" by DRC's late dictator Mobutu Sese Seko, she said. Mobutu ruled for more than 30 years and was overthrown in 1997.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.