Amnesty International has warned that the executions of 12 Saudi Shi'ite Muslim prisoners could be imminent, after they were sent to a secretive state security body that reports directly to the king.
The men, who were sentenced to death in 2016 after being convicted of spying for Iran in a mass trial, have been transferred to the Presidency of State Security, the human rights group said. They could be executed once the king ratifies their sentences.
"The families of the men are terrified by this development," Amnesty Middle East Director Heba Morayef said.
"Given the secrecy surrounding Saudi Arabia's judicial proceedings, we fear that this development signals the imminent execution of the 12 men."
The Saudi government could not be reached for comment on the cases.
Riyadh's human rights record has been in the spotlight since the disappearance of Saudi journalist Jamal Khashoggi at its Istanbul Consulate last month.
According to Amnesty, the men were sentenced to death after being convicted of spying for Iran in what it said was an unfair mass trial of 32 people arrested across Saudi Arabia in 2013 and 2014.
Shi'a have long complained of entrenched discrimination in majority-Sunni Muslim Saudi Arabia, a charge the authorities deny, and have periodically staged mass protests in the kingdom's eastern region, where many of them live.
In January 2016, the kingdom executed prominent Shi'ite cleric Sheikh Nimr al-Nimr, one of the most vocal critics of the Al-Saud royal family and a leader in the 2011 Arab Spring protests.
The execution led to violent anti-Saudi protests in Iran, which resulted in severance of diplomatic relation between Riyadh and Tehran.
An absolute monarchy, Saudi Arabia bans political parties and public forms of protest.
Dozens of intellectuals and clerics have been detained since last year in a crackdown on dissent. Women's rights activists also have been arrested despite the kingdom's lifting of a ban on women driving this year.