Saudi Arabia has beheaded 37 Saudi citizens, most of them minority Shiites, in a mass execution across the country for alleged terrorism-related crimes, and publicly pinned the executed body and severed head of a convicted Sunni extremist to a pole as a warning to others.

Key points: Saudi dissident Ali al-Ahmed described the executions as a politically motivated message to Iran

Saudi dissident Ali al-Ahmed described the executions as a politically motivated message to Iran The kingdom has been emboldened by Donald Trump's unwavering dedication to pressuring Iran's Shiite clerical leadership

The kingdom has been emboldened by Donald Trump's unwavering dedication to pressuring Iran's Shiite clerical leadership The Government defends such executions as a powerful tool for deterrence

The executions were likely to stoke further regional and sectarian tensions between rivals Saudi Arabia and Iran.

Saudi dissident Ali al-Ahmed, who runs the Gulf Institute in Washington, identified 34 of those executed as Shiites, based on the names announced by the Interior Ministry.

"This is the largest mass execution of Shiites in the kingdom's history," he said.

Amnesty International also confirmed the majority of those executed were Shiite men. The rights group said they were convicted "after sham trials" that relied on confessions extracted through torture.

It marked the largest number of executions in a single day in Saudi Arabia since January 2, 2016, when the kingdom executed 47 people for terrorism-related crimes in the largest mass execution carried out by Saudi authorities since 1980.

Among those executed three years ago were four Shiites, including prominent Shiite cleric Nimr al-Nimr, whose death sparked protests from Pakistan to Iran and the ransacking of the Saudi Embassy in Tehran. Saudi-Iran ties have not recovered and the embassy remains shuttered.

King Salman ratified by royal decree Tuesday's mass execution and that of 2016. The king, who has empowered son Crown Prince Mohammed bin Salman, has asserted a bolder and more decisive leadership style than previous monarchs since ascending to the throne in 2015.

Prince Mohammed bin Salman with King Salman bin Abdulaziz Al Saud. ( Saudi Royal Court: Bandar Algaloud )

The kingdom and its Sunni-led Arab allies have also been emboldened by US President Donald Trump's unwavering dedication to pressuring Iran's Shiite clerical leadership, which includes his decision to pull out of a nuclear agreement with Iran and re-impose punishing sanctions to cripple its economy.

Mr al-Ahmed described Tuesday's executions as a politically motivated message to Iran.

"They didn't have to execute these people, but it's important for them to ride the American anti-Iranian wave," he said.

Around 100 executions since start of 2019

The Saudi Interior Ministry's statement said those executed had adopted extremist ideologies and formed terrorist cells with the aim of spreading chaos and provoking sectarian strife.

It said the individuals had been found guilty according to the law and ordered executed by the Specialised Criminal Court in Riyadh, which specialises in terrorism trials, and the country's High Court.

The individuals were found guilty of attacking security installations with explosives, killing a number of security officers and cooperating with enemy organisations against the interests of the country, the Interior Ministry said.

The statement did not say in which city of Saudi Arabia the public display took place.

Amnesty said 11 of the men were convicted of spying for Iran and sentenced to death after a "grossly unfair trial". At least 14 others executed were convicted of violent offences related to their participation in anti-Government demonstrations in Shiite-populated areas of Saudi Arabia in 2011 and 2012.

The Interior Ministry said the body of one of the executed men — Khaled bin Abdel Karim al-Tuwaijri — was publicly pinned to a pole.

He appears to have been convicted as a Sunni militant, though the Government did not give a detailed explanation of the charges against each individual executed.

The Government defends such executions as a powerful tool for deterrence.

Those executed hailed from Riyadh, Mecca, Medina and Asir, as well as Shiite Muslim-populated areas of the Eastern Province and Qassim. The executions also took place in those various regions.

It brings the number of people executed in Saudi Arabia since the start of the year to around 100, according to official announcements. Last year, the kingdom executed 149 people, most of them drug smugglers convicted of non-violent crimes, according to Amnesty's most recent figures.

AP