Saudi Arabia plans to soon execute more than 50 people for "terrorist crimes," according to Amnesty International, which questioned the fairness of some of the trials and accused the government of "using the guise of counter-terrorism to settle political scores."

On Thursday, 55 people were awaiting execution for "terrorist crimes" that killed more than 100 civilians and 71 security personnel, according to Reuters. A semi-official Saudi newspaper al-Riyadh reported on Monday that 52 people would soon be put to death, but later deleted the report, Okaz reported

Some of the people awaiting execution are thought to be pro-democracy Shia activists who protested against the Sunni majority government, according to BBC.

"Among those who are at imminent risk of execution are these six Shi'a Muslim activists who were clearly convicted in unfair trials. It is clear that the Saudi Arabian authorities are using the guise of counter-terrorism to settle political scores," said James Lynch, deputy director of the Middle East and North Africa Program at Amnesty International.

Saudi newspapers reported that those facing execution include "al-Qaeda terrorists," who were accused of attempting to overthrow the government and conducting attacks with small arms, as well as Shia activists from the Awamiya area, a town where Shia protesters have clashed with the Sunni government since 2011.

The Awamiya residents were reportedly convicted of sedition, attacking security personnel and interfering in Bahrain, according to BBC. Awamiya's Shia minority have accused the Sunni monarchy of widespread discrimination.

"Three of those six activists were sentenced for 'crimes' committee while they were children and have said that they were tortured to confess," Lynch continued.

The juvenile offenders are Abdullah al-Zaher, Hussein al-Marhoon and Ali al-Nimr, who was sentenced to be crucified and beheaded, according to the International Business Times. They were arrested following protests calling for political reform.

Amnesty estimates that at least 151 people have been executed in Saudi Arabia so far in 2015, the highest figure recorded since 1995. In 2014, the reported number of executions was 90.

"Saudi Arabia's macabre spike in executions this year, coupled with the secretive and arbitrary nature of court decisions and executions in the kingdom, leave us no option but to take these latest warning signs very seriously. These executions must not go ahead and Saudi Arabia must lift the veil of secrecy around its death penalty cases, as part of a fundamental overhaul of its criminal justice system," Lynch said.

"Beheading or otherwise executing dozens of people in a single day would mark a dizzying descent to yet another outrageous low for Saudi Arabia, whose authorities have continued to show stone-faced cynicism and even open defiance when authorities and ordinary people around the world question their sordid record on the use of the death penalty."

Saudi Arabia justifies the death sentences under Sharia law and insists the offenders have received fair trials.