The French president, Emmanuel Macron, has said he is concerned about the “arbitrary detention” and health of Boualem Sansal, days after the French-Algerian author began a hunger strike over his imprisonment in Algeria.

On Tuesday, Pen America issued a statement calling for the immediate release of 75-year-old Sansal, noting that “his hunger strike adds to grave concerns for his wellbeing”.

In November, the writer was arrested on national security charges and subsequently hospitalised. A group of prominent writers including Salman Rushdie, Annie Ernaux, Wole Soyinka and Leïla Slimani signed a statement calling for his release.

Macron has spoken out about Sansal’s detention before, telling French ambassadors in January that Algeria was “dishonouring itself” by holding the writer.

His latest comments came on Friday during a speech in Porto, Portugal, in which he said that Sansal’s imprisonment was among the issues that needed settling before confidence between France and Algeria could be fully restored, according to Reuters.

Relations between France and its former colony have become increasingly hostile in recent months over immigration and a sovereignty dispute over Western Sahara, which Algeria has long said should be independent. Last summer, Macron sparked anger in Algiers when he backed Morocco’s plan for the territory to come under Moroccan control.

Sansal’s arrest was linked to comments the writer had made to the far-right French outlet Frontières in which he backed the argument that Morocco’s land was truncated by colonial France in the 19th century to the benefit of what would become Algeria.

Sansal was once an Algerian civil servant, but was driven to become a writer during the Algerian civil war of the 1990s. His books include An Unfinished Business, his first to be translated into English, and 2084, for which he won the Grand Prix du Roman.

Sansal has in recent years become popular with rightwing figures for his position on Islam, with Marine Le Pen calling him a “courageous opponent of Islamism” after his arrest. Sandrine Rousseau – a member of the green party Europe Écologie Les Verts, denounced his imprisonment, but called his views a “form of supremacism”.

“Writers like Boualem Sansal do not belong behind bars,” said Karin Karlekar, Pen America’s director of Writers at Risk, on Tuesday. “Algeria must honour its international obligations, uphold his human rights, and the rights of all detained writers in the country.”