A journalist detained in Eritrean prison without trial for 23 years has won a Swedish human rights prize for his commitment to freedom of expression.

Dawit Isaak, who holds dual Eritrean-Swedish citizenship, was given the Edelstam Prize "for his... exceptional courage", the foundation behind the award said in a statement.

Dawit was one of the founders of Setit, Eritrea's first independent newspaper.

He was detained in 2001 after his paper published letters demanding democratic reforms.

Dawit was among a group of about two dozen individuals, including senior cabinet ministers, members of parliament and independent journalists, arrested in a government purge.

Over the years, the Eritrean government has provided no information on his whereabouts or health, and many who were jailed alongside him are presumed dead.

The Edelstam Prize, awarded for exceptional courage in defending human rights, will be presented on 19 November in Stockholm.

Dawit's daughter, Betlehem Isaak, will accept the prize on his behalf as he remains imprisoned in Eritrea.

His work with the Setit included criticism of the government and calls for democratic reform and free expression, actions that led to his arrest in a crackdown on dissent.

The Edelstam Foundation has called for Dawit's release, urging the Eritrean authorities to disclose his location and allow him legal representation.

"Dawit Isaak is the longest detained journalist in the world. We are very concerned about his health and his whereabouts are unknown, he is not charged with a crime, and he has been denied access to his family, consular assistance, and the right to legal counsel – effectively, it is an enforced disappearance," said Caroline Edelstam, the chair of the Edelstam Prize jury.

His "indefatigable courage stands as a testament to the principle of freedom of expression."

The Edelstam Foundation also urged the international community to pressure Eritrea for Dawit's release and to advocate for human rights reforms.

The Edelstam Prize honours individuals who show exceptional bravery in defending human rights, in memory of Swedish diplomat Harald Edelstam.

Eritrea is the only African country without privately owned media, having shut down its private press in 2001 under the pretext of "national security".

Dawit, who fled to Sweden in 1987 during Eritrea’s war for independence, returned after the country gained independence in 1993 after becoming a Swedish citizen.

There have been no elections in Eritrea since its independence, and President Isaias Afwerki has held power for nearly 31 years.