A Bangladeshi professor internationally respected for his work on extremism has gone missing, police said on Thursday, with activists fearing the worst amid a spate of disappearances in recent months.
Mubashar Hasan, an assistant professor of political science at Bangladesh's North South University (NSU), has not been seen since Tuesday afternoon, his family said.
"We are very concerned. We hope law enforcement agencies will find him and return him to us," his uncle Monzur Hossain told AFP.
Hossain said his nephew, a former journalist, had become increasingly concerned about his safety just before his disappearance.
Hasan had installed CCTV cameras around his home just last week after an unidentified man paid him a visit at home, his uncle said.
Police said Hasan's mobile phone was switched off early Tuesday evening after the prominent professor of political Islam attended a conference.
"We are trying our best to find him. There is no shortage of sincerity on our part," Anwar Hossain, deputy commissioner of Dhaka Metropolitan Police, told AFP.
Rights groups in Bangladesh say Hasan disappearance is the ninth high-profile case since July, with opposition political figures, a businessman and journalists among others to vanish.
"He has done some research on Islamist extremism in Bangladesh. His disappearance could be linked to his work," prominent rights activist Nur Khan Liton told AFP.
Hasan joined NSU, Bangladesh's most prestigious private university, after completing a doctorate overseas on political Islam in Bangladesh.
His research on extremism in Bangladesh -- a Muslim-majority nation plagued by homegrown militancy -- has been published in respected journals and international media.
More than a dozen progressive academics, bloggers and rights activists have been murdered by militant groups in Bangladesh in recent years, most in brutal machete attacks.
Dozens of Islamist extremists have been killed and 200 suspects arrested in the government offensive against extremism since July last year, when militants killed 22 hostages, including 18 foreigners, at an upmarket cafe in Dhaka.
Opposition parties have accused Prime Minister Sheikh Hasina's government of arresting tens of thousands of their supporters and activists since 2014, when they boycotted a controversial general election amid concerns it would be rigged.
The government has also been accused of enforced disappearances and unofficial detention of critics and opponents in secret jails.