A general view of Riyadh city, Saudi Arabia, February 20, 2022. [Reuters, Mohammed Benmansour]

Saudi Arabia executed 81 men on Saturday, including seven Yemenis and one Syrian, for terrorism and other offences including holding "deviant beliefs", authorities said, in the biggest mass execution in decades.

The number dwarfed the 67 executions reported in the kingdom in all of 2021 and the 27 in 2020.

"These individuals, totalling 81, were convicted of various crimes including murdering innocent men, women and children," the interior ministry said in a statement.

"Crimes committed by these individuals also include pledging allegiance to foreign terrorist organisations, such as ISIS (Islamic State), al-Qaeda and the Houthis," it added.

Some travelled to conflict zones to join "terrorist organisations", the statement said.

The ministry did not say how the executions were carried out.

The men included 37 Saudi nationals who were found guilty in a single case for attempting to assassinate security officers and targeting police stations and convoys, the ministry added.

The kingdom executed 63 people in one day in 1980, a year after militants seized the Grand Mosque in Mecca, according to state media reports.

A total of 47 people, including prominent Shi’ite Muslim cleric Nimr al-Nimr, were executed in one day in 2016.

Rights groups have accused Saudi Arabia of enforcing restrictive laws on political and religious expression, and criticised it for using the death penalty, including for defendants arrested when they were minors.

Saudi Arabia denies accusations of human rights abuses and says it protects its national security according to its laws.

SPA said the accused were provided with the right to an attorney and were guaranteed their full rights under Saudi law during the judicial process