Amnesty International has criticised Saudi Arabia for excessive use of the death penalty, with 175 judicial killings carried out in the last 12 months.
The report claims that in the first six months of 2015, 102 judicial killings have been carried out, compared with 90 in all of 2015, an average of one execution every two days.
It alleged that many people are being executed for offences which do not deserve the death penalty, with the sentence applied for offences including adultery, apostasy, and witchcraft, as well as drugs offences and murder under the kingdom's strict interpretation of Sharia law.
Some victims sentenced to death are denied access to a lawyer and are forced to confess under torture, according to the report. It claims that among those executed were juvenile offenders and people with mental disabilities.
"Saudi Arabia's faulty justice system facilitates judicial executions on a mass scale," Said Boumedouha, acting director of Amnesty's Middle East and North Africa program, said in a statement.
Saudi Arabia has one of the highest execution rates in the world, with only China and Iran carrying out more judicial killings. Most are executed by beheading, and some are killed by firing squad.
Almost half those put to death were foreign nationals, with many denied access to translators at trial and made to sign legal documents, including confessions, they did not understand.
The report argues that Saudi Arabia's Sharia-based justice system lacks a clear definition of offences and punishments, "leading to vast discrepancies and in some cases arbitrary rulings".
The report highlights the case of two sets of brothers from extended families convicted on drugs charges after allegedly receiving large quantities of marijuana, and were forced to confess after being beaten and deprived of sleep.
"Sentencing hundreds of people to death after deeply flawed legal proceedings is utterly shameful," said Boumedouha.
"The use of the death penalty is horrendous in all circumstances, and is particularly deplorable when it is arbitrarily applied after blatantly unfair trials."
The Saudi government maintains all cases are tried in accordance with Sharia law, and with strict fair trial standards observed.