United Nations Secretary-General Ban Ki-moon has condemned the killing of Bangladeshi blogger Niladri Chattopadhyay Niloy.

In a statement issued yesterday, he voiced concern over these "gruesome" crimes and their impact on the exercise of freedom of expression in the country.

Ban Ki-moon called on the Government of Bangladesh to bring those responsible for the murder of Niloy and other bloggers to justice in an expeditious manner and act to ensure that all Bangladeshis can enjoy freedom of expression and all other human rights without fear, the statement read.

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Meanwhile, the European Union Delegation to Bangladesh also condemned in the strongest possible terms the vile aggression committed against Niloy.

"We present to his widow and other family members our sincere condolences," the EU delegation said in its statement.

In addition, two independent UN rights experts David Kaye, special rapporteur on freedom of expression and Christof Heyns, special rapporteur on extrajudicial executions, also joined voice in condemnation of the blogger killing.

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"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," they said in a news release.

The experts stressed that the organised targeting of critical voices aims at promoting a culture of silence and fear, and affects the society as a whole.

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"The Bangladeshi authorities must not only continue to strongly condemn these horrendous acts against freedom of expression, but should also ensure that their words are followed by more effective efforts to ensure greater accountability and prevent this kind of violence."

The EU statement read, "This being the fourth such savage assassination in less than 6 months, the intention of the perpetrators is clear to suppress the freedom of expression."

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"But we have learnt from history that the people of Bangladesh do not tolerate intimidation. Freedom of expression is, in the first place, an expression of freedom," added the statement.

"We urge all relevant official authorities to take immediate action against those responsible for these crimes, bring them to justice and prevent repetition of such barbaric acts." 

Unidentified assailants hacked to death blogger Niloy inside his house in the capital in broad daylight on Friday.

Niloy, 28, who also was a Gonojagoron Mancha activist, is the fourth blogger to have been killed this year by suspected Islamist militants.      

Four men armed with cleavers tricked into his Goran house in Khilgaon posing as potential tenants and then killed him in his bedroom, according to police and family members.