US justice officials on Thursday said a former Twitter worker convicted of spying for Saudi officials was sentenced to 3.5 years in prison.

Ahmad Abouammo was found guilty in August on criminal counts including money laundering, fraud, and being an illegal agent of a foreign government, according to a copy of the verdict.

Prosecutors in federal court in San Francisco told jurors that Abouammo sold Twitter user information for cash and an expensive watch some seven years earlier.

"This case revealed that foreign governments, here, the Kingdom of Saudi Arabia will bribe insiders to obtain the user information that is collected and stored by our Silicon Valley social media companies," US attorney Stephanie Hinds said in a statement.

"This sentence sends a message to insiders with access to user information to safeguard it, particularly from repressive regimes, or risk significant time in prison."

The defense team for 45-year-old Abouammo contended in court that he did nothing more than accept gifts from free-spending Saudis for simply doing his client management job.

"The evidence shows that, for a price and thinking no one was watching, the defendant sold his position to an insider of the crown prince," US prosecutor Colin Sampson said in final remarks to the jury.

Defense attorney Angela Chuang countered that while there certainly appeared to be a conspiracy to get revealing information about Saudi critics from Twitter, prosecutors failed to prove Abouammo was part of it.

Abouammo quit Twitter in 2015 and took a job at e-commerce titan Amazon in Seattle, where he lives, according to court documents.

Jurors found Abouammo guilty on 6 of the 11 charges against him.

Chuang conceded to the jury that Abouammo did violate Twitter employee rules by not telling the San Francisco-based company that he had received $100,000 in cash and a watch valued at more than $40,000 from someone close to the Saudi crown prince.

However, she downplayed the significance of the gift, saying it amounted to "pocket change" in a Saudi culture known for generosity and lavish presents. US district court Judge Edward said while pronouncing the sentence that "exposing dissident information is a serious offense," and ordered Abouammo to forfeit the value of "bribes" received, according to prosecutors.

Abouammo is to begin serving his sentence at the end of March.

Prosecutors accused Abouammo and fellow Twitter employee Ali Alzabarah of being enlisted by Saudi officials between late 2014 and early the following year to get private information on accounts that were critical of the regime. The then-Twitter workers could glean email addresses, phone numbers, birth dates and other private data to identify people behind anonymous accounts, prosecutors said.

Alzabarah, a Saudi national, is being sought on a charge of failing to register in the United States as an agent of a foreign government as required by United States law, according to an FBI statement.