One of the convicts was crucified, according to an interior ministry statement carried by the Saudi Press Agency (SPA).
In Saudi Arabia, crucifixion means the body of someone executed is strung up and put on display as a deterrent to others.
The statement listed the names of the 37 Saudi nationals who were executed in various parts of the country.
The majority of those executed were Shia men, according to Amnesty International, which dismissed the legal proceedings that led to the convictions as “sham trials that violated international fair trial standards which relied on confessions extracted through torture.”
The kingdom has repeatedly denied allegations of torture.
Those executed include 11 men convicted of spying for Iran, and at least 14 others who were convicted of violent offenses related to participation in anti-government demonstrations in the country’s restive Eastern Province between 2011 and 2012, according to Amnesty.
One of the men listed in Tuesday’s government statement was Abdulkareem al-Hawaj, who, according to Amnesty, was arrested at the age of 16 and convicted of offenses related to his involvement in anti-government protests.
He was charged with shooting members of security forces, using Molotov cocktails, and other acts of violence related to protests Leif took part in in the Eastern Province town of Awamiya, according to Saudi Arabia’s letter to the UN.
CNN has contacted the Saudi authorities for comment on Leif’s execution.
Referring to the executions overall, a Saudi official told CNN “justice was served” and alluded to a recently foiled attack on an intelligence center in the kingdom’s Zulfi Province as proof that terror groups “continue to target the kingdom and its people.”
“The Kingdom of Saudi Arabia has long ago adopted a zero tolerance policy towards terrorists who spill the blood of the innocent, threaten the national security of the kingdom and distort our great faith,” the official said. “The convicted criminals who were executed today had their day in court and were found guilty of very serious crimes.”
An official from the US State Department said it has urged the kingdom to “ensure fair trial guarantees.”
“We have seen these reports. We urge the government of Saudi Arabia, and all governments, to ensure trial guarantees, freedom from arbitrary and extrajudicial detention, transparency, rule of law, and freedom of religion and belief,” the US official told CNN.
“We have spoken out publicly about many of our concerns, including in the Human Rights and International Religious Freedom reports, and continue to do so in our private diplomatic engagements as well,” the official added.
Mass executions in Saudi Arabia
Saudi Arabia has one of the highest death penalty rates in the world.
It carried out one of its largest mass executions in January 2016, when 47 people were put to death, including prominent Shia leader Nimr al-Nimr. The executed prisoners were accused of terrorism and having extremist ideology.
Since Prince Mohammed bin Salman first emerged onto the kingdom’s political scene in 2015, he has overseen an intensified crackdown on dissent. He began his political career as defense minister and was elevated to Crown Prince in 2017.
In recent years, the Crown Prince has ordered the rounding up of scores of activists, high-profile clerics, analysts, businessmen and princes, as well as women’s rights defenders who were allegedly tortured and whom authorities accuse of “suspicious contact” with foreign entities.
CNN’s Sarah El Sirgany, Kylie Atwood and Ruba Alhenawi contributed to this report.