Dubai: At least 33 of the 37 Saudis executed by the kingdom in a single day belonged to the Sunni-dominated country's Shiite minority, Human Rights Watch said Wednesday.
The men were executed on Tuesday after being convicted of terrorism, according to the official Saudi Press Agency.
"Thirty-three we know for sure are Shiites," HRW researcher Adam Coogle told AFP.
The interior ministry said some of those executed were accused of "inciting sectarian strife", a charge often used in Saudi Arabia against Shiite activists.
Rights group Amnesty International also said most of those executed were Shiite men.
They were "convicted after sham trials that violated international fair trial standards (and) which relied on confessions extracted through torture", it said in a statement.
The executions were "yet another gruesome indication of how the death penalty is being used as a political tool to crush dissent" from within the Shiite minority, said Amnesty's Middle East research director Lynn Maalouf.
The rights watchdog said 11 of those executed were convicted of spying for Iran, while at least 14 others were sentenced in connection with anti-government protests in the Eastern Province between 2011 and 2012.
Among those executed was Abdulkareem al-Hawaj, who was only 16 at the time of his arrest, it said.
At least 100 people have been executed in Saudi Arabia since the start of the year, according to data released by SPA.
The Eastern Province -- home to the country's Shiite minority -- has seen bouts of unrest since 2011 when protesters emboldened by the Arab Spring took to the streets demanding an end to alleged discrimination by the Sunni-dominated government.
Although no official figures exist, Shiites make up an estimated 10-15 percent of the ultra-conservative kingdom's population of 32 million.