SANAA - Human Rights Watch and Amnesty International on Friday urged Yemen's Shiite Huthi rebels to free a political commentator they detained this week in Sanaa.
Hisham al-Omeisy, 38, who has criticised both Huthi-imposed restrictions on independent organisations and actions by a Saudi-led coalition battling the rebels, was detained on Monday, the two organisations said in separate statements.
"Yemen more than ever needs activists like Hisham al-Omeisy to bring attention to the devastation that war, famine and disease have wrought on the country and its people," HRW's Middle East director Sarah Leah Whitson said.
"Huthi authorities should immediately release al-Omeisy and return him safely to his family."
Amnesty's Samah Hadid called Omeisy "a prisoner of conscience, whose only 'crime' is peacefully exercising his right to freedom of expression".
"He must be released immediately," she said.
HRW said it has documented 66 cases of arbitrary arrest by the rebels, who control Sanaa and parts of northern Yemen. Two of the captives died in detention and 11 were tortured or ill-treated, it said.
The Iran-backed Huthis, allied with troops loyal to ex-president Ali Abdullah Saleh, are fighting government forces backed by a Saudi-led Arab military coalition.
More than 8,400 people -- over half of them civilians -- have been killed since the coalition intervened in 2015.
The fighting has caused a humanitarian catastrophe which the UN says is the world's worst, pushing seven million people to the brink of famine and sparking a cholera outbreak that the World Health Organization says has killed 2,000 people.