Over 150 writers—a growing alliance that includes Margaret Atwood, Yann Martel, Salman Rushdie, and Colm Tóibín—added their names to a letter that condemns the murder of three secular bloggers in Bangladesh this year. The letter demands that the Bangladeshi government bring the perpetrators to justice and protect and support bloggers and writers at risk “in accordance with Bangladesh’s obligations under national and international law.”

Among those killed were blogger Ananta Bijoy Das, who was hacked to death on May 12th by four masked attackers wielding machetes; Washiqur Rahman Babu, who, in March, was also killed by militants with machetes; and Avijit Roy, who was brutally attacked in February alongside his wife, Rafida Ahmed Bonya, and died while in transport to the hospital. His wife survived, but was in critical condition.

The letter, initiated by PEN International and English PEN, reads, “Freedom of expression is a fundamental right under Bangladesh’s constitution, as well as one of the rights under the Universal Declaration of Human Rights. We call on the Bangladeshi authorities to swiftly and impartially investigate Ananta Bijoy Das’s death as well as the murders of Avijit Roy and Washiqur Rahman Babu, and ensure the perpetrators are brought to justice.”

Martel said to The Guardian in an email that religious extremism is “the harshest and most personal threat” to writers. “Why wouldn’t we defend them? An offence is an offence, and offences, if unchecked, are contagious. What happens over there will eventually have an effect here, regardless of where there and here are.”