Unidentified attackers hacked to death a university professor in Bangladesh on Saturday.

Sakhawat Hossain, a fellow English professor from the university and a friend, said the slain Rajshahi University teacher Rezaul Karim Siddique, 58, played the Tanpura, a musical instrument popular in South Asia, and wrote poems and short stories, reports AFP.

‘He used to lead a cultural group called Komol Gandhar and edit a bi-annual literary magazine with the same name. But he never wrote or spoke against religion in public,’ Hossain told AFP.

Police said Siddique was the fourth professor from Rajshahi University to have been murdered. In February, a court handed down life sentences to two Islamist militants for the murder of another professor, Mohammad Yunus.

The recent killings have sparked outrage at home and abroad, with international rights groups demanding that the secular government protect freedom of speech in the Muslim-majority country.

Ansar al-Islam, a Bangladesh branch of Al-Qaeda in the Indian Subcontinent, this month claimed responsibility for the murder of 26-year-old Nazimuddin Samad, a law student who was killed on the streets of Dhaka, according to US monitoring group SITE.

Police, however, blamed the Ansarullah for the murder.

Bangladesh authorities have consistently denied that international Islamist networks such as Al-Qaeda or the Islamic State group, which recently claimed responsibility for the murders of minorities and foreigners, are active in the country.

A long-running political crisis in the majority Sunni Muslim but officially secular country has radicalised opponents of the government and analysts say Islamist extremists pose a growing danger.