The wife of an American blogger and critic of religious extremism who was hacked to death in Dhaka last month said that police stood nearby when the couple were attacked on a university campus in the Bangladesh capital. Avijit Roy, an engineer of Bangladeshi origin, was killed by machete-wielding assailants when returning from a book fair. His wife, Rafida Bonya Ahmed, suffered head injuries and lost a finger. "While Avijit and I were being ruthlessly attacked, the local police stood close by and did not act," Rafida told Reuters. "Now, we demand that the Bangladeshi government do everything in its power to bring the murderers to justice." Mohammad Masudur Rhaman, a deputy police commissioner of Dhaka Metropolitan Police, said authorities were investigating Rafida's claims. The U.S. Federal Bureau of Investigation (FBI) is also helping with investigations. Avijit's killing follows a string of attacks on secular bloggers in recent years in the Muslim-majority nation. Media group Reporters Without Borders rated Bangladesh 146th among 180 countries in a ranking of press freedom last year. Rafida urged the government to "stop a legal culture of impunity, where writers can be killed without the killers being brought to trial". Bangladesh's anti-terrorism unit said last week it had arrested Farabi Shafiur Rahman in connection with the attack. Rahman had previously been jailed for his ties to the extremist Hizbut Tahrir Islamist group.