YANGON (Reuters) - Myanmar wants to continue working with the United Nations on human rights but its investigator must be fair, the foreign ministry said on Thursday, a day after special rapporteur Yanghee Lee was barred from visiting the country.  Myanmar is still cooperating with the special rapporteur mechanism,  said Ministry of Foreign Affairs spokesman Kyaw Moe Tun.  But Ms Yanghee Lee s undertakings don t have impartiality and objectivity,  he said, adding that Myanmar had asked the United Nations to replace her with someone who knows Myanmar well and is both fair and impartial. Lee had been due to visit Myanmar next month to assess human rights across the country, including alleged abuses against Rohingya Muslims in Rakhine State, but on Wednesday she said she    had been barred from visiting for the rest of her tenure. She called for stronger international pressure to be exerted on Myanmar s military and said in a statement that the ban suggested something  terribly awful  was happening in the country. More than 650,000 Rohingya have fled into Bangladesh since Aug. 25, when attacks by Muslim insurgents on the Myanmar security forces triggered a sweeping counter-offensive by the army and Buddhist vigilantes.  Surveys of Rohingya refugees in Bangladesh by aid agency Medecins Sans Frontieres have shown at least 6,700 Rohingya were killed in Rakhine state in the month after violence flared up on Aug 25, the aid group said last week. The U.N. High Commissioner for Human Rights Zeid Ra ad al-Hussein has called the violence  a textbook example of ethnic cleansing  and said he would not be surprised if a court eventually ruled that genocide had taken place.  Myanmar has rejected accusations of ethnic cleansing, blaming most of the violence and torching of Rohingya villages on the Rohingya insurgents who attacked the security forces. Lee had planned to use her visit to find out procedures for the return of Rohingya refugees, and to investigate increased fighting in Kachin State and Shan State in northern Myanmar, where the army is battling autonomy-seeking ethnic minority insurgents. Kyaw Moe Tun, who is director general of the foreign ministry s International Organizations and Economic Department, said a statement released by Lee after her last visit in July  was not objective and not impartial .  If she comes again and does that, it is not easy to cooperate with us and have a positive attitude,  he said. Lee said in July that activists and journalists continued to be followed and questioned by state surveillance agents, and that her visit was beset by official snooping and access restrictions. The office of Myanmar leader Aung San Suu Kyi said at the time that it was  disappointed  with Lee s end-of-mission statement, which contained  many sweeping allegations and a number of factual errors . It did not give any details and did not directly address the issues of access or surveillance. 