Udendu was reportedly killed on his way to a printing press to supervise the printing of the monthly newspaper.
After his killing, an anonymous phone call was reportedly made to his elder brother, Chukwulozie, asking him to retrieve the body of his sibling at a location in the city.
However, the NUJ, in a statement on Tuesday by its President, Muhammad Garba, and National Secretary, Shu’aibu Leman, decried Udendu’s killing.
The News Agency of Nigeria had quoted Garba as saying on January 4 that 13 Nigerian journalists were killed while covering assignments in 2012.
The statement read in part, “This recent development is shocking to the union, as daily, there are clear signals of such attacks on media professionals who work mostly without any insurance cover. It is worth stressing that the freedom of thought and opinion is a precious human right, and it is next in importance only to the right to live.
“As professionals, whose responsibility is to monitor governance and hold government accountable to the masses, journalists now live in perpetual fear of being either arrested by security officials or attacked by faceless assailants without any just cause.”
The body described attacks on journalists and media outfits as “illegal”, saying they were aimed at restraining the freedom of information in the country.
The statement added, “Attacks on journalists and media equipment are illegal under international humanitarian law, but despite this, the Nigerian system remains mainly unable to ensure the security of lives and property, especially that of journalists whose professional calling involves exposing crime and criminality in society.
“This is very unacceptable and we therefore appeal to the concern authorities to ensure that such attacks are properly investigated and culprits brought to book.”
Meanwhile, Anambara State Commissioner of Police Ballah Nasaraw, said on Tuesday that his command would probe the killing of Udendu.