Reporters Without Borders said Friday it was "appalled" at a death sentence handed to a veteran journalist by a court in Yemen's rebel-held capital.
The court in Sanaa, which is controlled by Iran-backed Huthi insurgents, on Thursday found Yahya al-Jubaihi guilty of spying for neighbouring Saudi Arabia.
Reporters Without Borders (RSF) said it was the first death sentence issued against a journalist in Yemen.
"This Huthi-imposed death sentence sets a dangerous precedent for journalists in Yemen," said Alexandra El Khazen, the head of RSF's Middle East desk.
"Issued at the end of an unfair trial, it constitutes a grave violation of international law. We urge Huthi leaders to free this journalist at once," she said.
The Huthis hail from Yemen's Shiite-linked Zaidi minority in northern Yemen.
Since March 2015, oil-rich Saudi Arabia has been leading a deadly military intervention against the Huthis and their allies in the kingdom's impoverished neighbour.
The Huthis, supported by renegade troops loyal to former president Ali Abdullah Saleh, have controlled all government institutions in Sanaa since they overran the capital in September 2014.
Rival bodies loyal to internationally recognised president Abedrabbo Mansour Hadi operate out of second city Aden or from exile in Saudi Arabia.
Yemen's press union on Thursday condemned the sentence as "arbitrary" and accused the rebels of "targeting press freedom".
It said Jubaihi, 61, was seized from his home on September 6.
Press watchdogs and human rights groups have been deeply critical of the rebels' treatment of journalists as the conflict in the Arabian peninsula country has escalated over the past two years.
Eight reporters were killed in Yemen last year, according to the International Federation of Journalists.
RSF says at least 16 journalists and media workers are currently being held by armed groups in Yemen including the Huthis and Al-Qaeda.
Yemen is ranked 170th out of 180 countries in the organisation's 2016 World Press Freedom Index.