An ally of Ivory Coast's incumbent President Laurent Gbagbo has warned UN peacekeepers they could be treated as rebels if they remain in the country after being told to leave. Mr Gbagbo accuses the UN of siding with his rival Alassane Ouattara and ordered them out of the country. The UN says Mr Ouattara won last month's poll and has urged all parties to recognise him as president. It has extended the mandate of its 10,000-strong force by six months. Mr Gbagbo says the polls were rigged in rebel-held areas of the north and was declared the winner by the Constitutional Council. But the UN mission in Ivory Coast, which was involved in organising the election, backed the electoral commission in saying Mr Ouattara had won. At least 50 people have been killed in violence linked to the dispute, the UN says, amid fears of a return to civil war. Mr Gbagbo's Interior Minister, Emile Guirieoulou, said of the UN mission: "If, against our will, they want to keep this force in our country, we won't co-operate with them. "And if they choose to have authorities other than the legal authorities of the country, they become part of the rebellion." He also dismissed reports of a mass grave in the main city Abidjan. "It's lies. All that to get some sympathy." On Monday, UN special envoy to Ivory Coast Choi Young-jin said the UN had been prevented from investigating the reports. The UN also says it has received hundreds of reports of people being abducted by armed men at night. Some have later been found dead. Gbagbo exile offer UN peacekeeping chief Alain Le Roy told the AFP news agency that UN troops were being harassed by pro-Gbagbo groups. "They want to cut all of our fuel. They are forcing us to leave the apartments we use," Mr Le Roy said. UN troops are guarding the luxury Hotel Golf where Mr Ouattara has been based since the election and he meets members of the cabinet he has named. Western - as well as African countries - have backed Mr Ouattara. Nigeria's Minister of State for Foreign Affairs Aliyu Idi Hong told the BBC that it would be willing to let Mr Gbagbo go into exile in Nigeria. The European Union says it will this week issue a travel ban on Mr Gbagbo and 18 of his closest allies, including his wife. It is also working on freezing any assets he may have in the EU. The election, delayed for five years, was supposed to reunify the world's largest cocoa producer, which has been divided since 2002. Source: BBC