Margaret Atwood has written to Asli Erdoğan on her 91st day behind bars to tell the imprisoned Turkish novelist that her “words still shape the fight for freedom and the right to free expression”.

The Canadian Booker prize winner is one of a group of authors sending messages of solidarity to five writers currently in prisons around the world. The letters are intended to mark the Day of the Imprisoned Writer, which has been commemorated on 15 November by PEN International and members of PEN from around the world since 1981. PEN said that in the 12 months since last year’s event, at least 35 writers have been killed for their work.

This year, PEN International is highlighting five cases which it says are “emblematic of the kinds of challenges and dangers writers face simply in the course of carrying out their free expression work”.

As well as the esteemed Turkish novelist Erdoğan, who was arrested in August and charged with “membership of a terrorist organisation” and “undermining national unity”, PEN pointed to the cases of the Egyptian novelist and journalist Ahmed Naji, who is serving a two-year prison sentence for “violating public modesty” following the publication of parts of his 2014 novel Istikhdam al-Hayat (The Use of Life), and the Honduran Cesario Alejandro Félix Padilla Figueroa, who it says has faced prosecution and harassment for his part in ongoing student protests.

The writers’ organisation also highlighted the situations of Dareen Tatour, a Palestinian citizen of Israel who is currently under house arrest and standing trial on charges of “support for a terrorist organisation” in connection with her poetry and social media activity, and Chinese publisher Gui Minhai, who disappeared in October 2015 and reappeared three months later to make a confession on state-controlled television, saying that he had voluntarily surrendered himself to Chinese authorities.

Each of the persecuted writers has been sent a message of solidarity by another author, with Atwood writing to Erdoğan to tell her that “even through the concrete walls of your prison, beyond the guards, the barbed wire, the locks and keys, we can still hear your voice”.

“Although you are in prison, you are not alone: you have the entire PEN community of writers from around the world fighting for your freedom. They will continue to hope for you, and they will not stop working for you until you are free,” wrote Atwood.

“I have faith that you will very soon be free. I hope that you will find yourself in a Turkey where you can write and speak without fear and censorship, a Turkey that celebrates diversity of thought and opinion. I hope you will live in a Turkey that is proud of the voices of its talented thinkers, writers, and artists who have reached so many admirers far beyond its borders. I hope you will live in a Turkey that is proud of its democracy – a Turkey that is proud of voices like yours.”

The authors Salil Tripathi, Hanan al-Shaykh, Gioconda Belli and Jennifer Clement have written letters to Gui, Naji, Padilla and Tatour respectively.

“Writers should be writing when they want to write. They should not be in prison. And yet, around the world, hundreds of writers are in jail today, and many more face intimidation and persecution because what they express upsets the authorities, offends the powerful, and unnerves governments,” said Tripathi, chair of PEN International’s writers in prison committee.

“Writers are the conscience-keepers of society; they must remain free – their place is not in prison, but with pen and paper, with typewriters, with their keyboards. And on this day, every year, the entire PEN community says in one voice that we will continue to fight for freedom for any writer, anywhere in the world, who is prevented from doing his or her work.”