A law student who posted pro-atheism comments on social media has been murdered, Bangladeshi police said, in the latest incident in a series of killings of secular activists and bloggers in the country.

Dhaka Metropolitan Police Assistant Commissioner Nurul Amin said at least three men riding on a single motorbike carried out the killing on Wednesday night. No group immediately claimed responsibility.

Al Jazeera's Tanvir Chowdhury, reporting from Dhaka, said 28-year-old Nazimuddin Samad was the seventh secular activist who has been killed.

"The men on the motorbike first hit him with machetes. Then they shot him to make sure he was dead," Chowdhury said.

Police suspected that Samad had been targeted for his outspoken atheism in the Muslim-majority country, and for supporting a 2013 movement to demand capital punishment for war crimes involving the country's independence war against Pakistan in 1971.

The national Dhaka Tribune newspaper reported that the assailants shouted "Allahu Akbar" (God is Greatest) as they attacked Samad on a busy road near Dhaka's Jagannath University, where he was a law student.

Samad had only recently arrived in Dhaka from the northeastern city of Sylhet to study law.

Killing spree

Last year, assailants hacked to death at least four atheist bloggers and a secular publisher in a long-running series of targeted killings of secular activists.

Police arrested members of a banned group called the Ansarullah Bangla Team over those murders, although none have yet been prosecuted.

Q&A: Why are bloggers being killed in Bangladesh?

Imran Sarker, who leads Bangladesh's largest online secular activist group, said Samad had joined nationwide protests in 2013 against leaders accused of committing war crimes during the country's war of independence.

"He was a secular online activist and a loud voice against any social injustice. He was against Islamic fundamentalism," said Sarker, head of the Bangladesh Bloggers Association.