Four Saudi men have been sentenced to death for their role in one of the kingdom's "bloodiest terror cells", official SPA news agency has reported.
The agency said late Sunday that a special criminal court in Riyadh jailed "as many as 20" others for between two and 23 years for a variety of crimes.
These included embracing "deviant" thinking contrary to the Koran, a term usually used in Saudi Arabia to refer to Al-Qaeda suspects.
The defendants were also convicted of fighting abroad and purchasing five tonnes of aluminium nitrate -- which can be used to make explosives.
They were also found guilty of booby-trapping vehicles to kill policemen, carrying out suicide bombings inside the country, planning to explode oil pipelines and killing foreigners as well as Islamic religious leaders, SPA said.
The convicted were given 30 days to appeal the verdicts.
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SPA did not say when the offences occurred but the sentences are the latest in a series since authorities in 2011 established specialised courts to try Saudis and foreigners accused of belonging to Al-Qaeda or involvement in deadly attacks in the kingdom from 2003-2006.
These included assaults on housing compounds where foreigners lived, and led to a crackdown.
Last week, another court in Riyadh sentenced two men to death and jailed 13 others for killing a policeman and forming an Al-Qaeda cell in prison, SPA reported.
The sentences come after regional heavyweight Saudi Arabia earlier this month agreed with other Arab states to back Washington against Islamic State group jihadists.
The group has declared a "caliphate" straddling Iraq and Syria, where it controls swathes of territory.
It is regarded as the most violent and powerful in modern jihad, executing hundreds of Iraqis and Syrians, as well as foreign hostages in a campaign that has forced more than a million people from their homes.
Saudi Arabia's top cleric has branded Al-Qaeda and the IS group Islam's "enemy number one".
King Abdullah decreed in February jail terms of up to 20 years for citizens who travel to fight abroad. The country is seeking to deter young Saudis from becoming jihadists after Syria's conflict attracted several hundred Saudi nationals.