Ten international rights organisations have urged Oman's Sultan Qaboos to revoke an order to close a newspaper and end a crackdown by authorities on journalists and activists.
A court last month upheld a government order to permanently close the Azamn daily over an article about suspected corruption within the judicial system.
Its editor-in-chief Ibrahim al-Maamari and his deputy Yousef al-Haj were each sentenced to three years' jail and a colleague, Zaher al-Abri, got one year.
They were convicted of disturbing public order, undermining the prestige of the state and misusing the internet, judicial sources have said.
All three are on bail pending a hearing on November 7.
"These harsh sentences are a clear attempt to hinder the work of journalists and to curtail the right to freedom of expression and opinion in Oman," said the joint statement by 10 watchdogs including Reporters Without Borders (RSF) and the Committee to Protect Journalists.
"The imprisonment of journalists whose only crime was to exercise their profession in a legitimate manner and the censorship of this story do not bode well for the future of journalism and civil liberties in the sultanate," they added.
The groups urged the Gulf state's ruler to use his influence to "protect freedom of the media and freedom of speech...(and) revoke the closure order of Azamn newspaper".
The signatories called for the sentences against the journalists to be revoked and also for two online activists arrested for expressing their support for the Azamn three to be released "immediately and unconditionally".
They urged Qaboos to ensure that the internal security service "stops its attacks on media freedom and freedom of expression and its targeting of journalists, online activists and other human rights defenders".
Also among the signatories are the International Federation for Human Rights and the Gulf Centre for Human Rights.
Oman ranks 125th out of 180 countries in RSF's 2016 World Press Freedom Index.
