US prosecutors allege the kingdom paid former Twitter employees in luxury watches and cash in exchange for personal information about critics. Millions of Saudis are active on the social media platform.
Two former Twitter employees and a former employee of the Saudi royal family faced charges in the US of spying on critics of Saudi Arabia in exchange for payment.
Saudi citizen Ali Alzabarah and US citizen Ahmad Abouammo, who used to work for Twitter, and were accused on Wednesday of working for the Kingdom of Saudi Arabia without registering as foreign agents.
The two former employees were alleged to have taken private user data and of prominent Saudi royal family critics and passed it on to the Saudi government with the help of Ahmed Almutairi, who acted as a go-between.
The targeted accounts included a news personality and a prominent government critic with over 1 million followers on the social media platform.
Abouammo was arrested in Seattle, Washington, while the other two are in Saudi Arabia.
On Wednesday the judge ordered Abouammo to remain in detention pending a hearing set for Friday, because of a "serious risk of flight."
The men accessed personal data of Saudi critics
The complaint against Abouammo detailed that he repeatedly accessed the Twitter account of two prominent critics of the Saudi royal family.
In one instance, he was able to view the email address and telephone number associated with the account. He also accessed personally identifiable information from another critic's account.
In return, Alzabarah and Abouammo both received thousands of dollars in compensation and other rewards, including an expensive designer watch.
"This information could have been used to identify and locate the Twitter users who published these posts," the US Justice Department said in a statement.
Twitter thanks the FBI but the Saudis remain silent
Microblogging site Twitter thanked the FBI and US Justice Department, which carried out the investigation.
"We recognize the lengths bad actors will go to try and undermine our service" said the company in a statement. "We understand the incredible risks faced by many who use Twitter to share their perspectives with the world and to hold those in power accountable."
The Saudi embassy in the US did not immediately respond to a request for comment.
According to Human Rights Watch Middle East researcher Adam Coogle, Twitter is the main platform for Saudis to express their views and about a third of the country's 30 million people are active users.
The complaint marked the first time that the oil-rich Gulf state and Washington ally has been accused of spying in the US, news agency AP reported.
The allegations come soon after the one-year anniversary ofthe murder of Jamal Khashoggi, the prominent Saudi critic who was killed at the Saudi consulate in Istanbul.