Amnesty International today urged Bangladesh authorities to ensure protection of activists and writers who are under threat.

Referring to yesterday's killing of secular activist Nazimuddin Samad, the human rights organisation said the latest killing is a grave reminder that "the authorities are failing to protect people exercising their right to freedom of expression".

Unidentified assailants hacked and shot Samad, 26, a law student of Jagannath University, to death in the capital's Hrishikesh Das Lane last night.

While no-one had yet to claim responsibility for the murder till filing of this report this evening, Amnesty said in a press release issued today that the killing fits the pattern of other similar attacks on secular activists by radical Islamist groups over the past year.

"There can be no justification for the brutal killing of Nazimuddin Samad, who has apparently paid with his life for nothing but being brave enough to speak his mind. This is not just a senseless murder, it is a blatant attack on the right to freedom of expression," said Champa Patel, South Asia director of the rights body.

Samad, a student activist who had organised campaigns for secularism on social media, was named on a "hit list" of 84 bloggers published by a group of radical Islamists in 2013, according to AI.

In 2015, at least five people – four bloggers and one publisher – were killed because of their secular opinions and writings.

"No one has yet been held to account for these killings and the Bangladeshi authorities have failed to strongly condemn the attacks. Instead, they have instructed secular activists to stop 'offending' religious sentiments through their writings. Dozens of other bloggers have been forced into hiding or exile, fearing for their lives," reads the AI press release.

"Bangladeshi authorities must categorically condemn these killings and take serious steps to end this horrific cycle of violence. Those responsible for the killings of secular activists must be held to account, anything less will send a signal that these attacks are tolerated and permitted by the government," said Champa Patel.

"The authorities must also ensure that those activists and writers who are under threat are effectively protected in accordance with their wishes."