Expressing condemn over the murder of secular blogger Niladri Chatterjee, the United Nations has said the violent killing of another critical voice in Bangladesh shows that serious threats to freedom of expression persist in the country.UN Special Rapporteurs on freedom of expression David Kaye and on extrajudicial executions Christof Heyns said in a statement.They also called for a prompt and thorough investigation into the killing."It is vital to ensure the identification of those responsible for this and the previous horrendous crimes, as well as those who may have masterminded the attacks," UNB quoted the UN Special Rapporteurs.The organized targeting of critical voices aims at promoting a culture of silence and fear, and affects the society as a whole, they said.They reiterated their call on the Bangladeshi authorities to consider specific initiatives to prevent the recurrence of attacks against writers and activists.Also known as Niloy Neel on blogging platforms and Facebook, Niladri Chatterjee was killed with machetes by four unidentified assailants at his Goran residence in Dhaka around 1:30pm Friday.Niloy, who worked at an NGO, had rented the flat on the fourth floor of a building in the area two years back, identifying himself as a Muslim named Niloy Chowdhury. He used to stay with his wife Ashamoni and sister-in-law.Recently he was trying to leave the country out of fear as three secularist activists had been killed by the militants since February. He also received threats several times.A group named Ansar Al Islam, believed to be banned militant group Ansarullah Bangla Team, has claimed responsibility for the murder. In an email sent to the media in the afternoon, they said that Niloy had been killed for his blasphemous activities, and warned others of similar consequences for demeaning the Almighty and the Prophet. -DT