WASHINGTON (Reuters) - The US Justice Department has accused two former Twitter employees of spying for Saudi Arabia on accounts critical of its policies, The Washington Post reported on Thursday.

The charges came a day after the arrest of the American citizen Ahmed Abu Amo, a former employee in Twitter, the first defendant. The second defendant, a Saudi national named Ali al-Zubara, was charged with accessing personal information to more than 6,000 Twitter accounts in 2015.

The Ministry of Justice said the defendants worked together for the Saudi government and the royal family to reveal the identities of opposition account holders on Twitter.

Among the accounts targeted was the account of Saudi dissident Omar Abdel Aziz, who was close to the late Saudi journalist Jamal Khashoggi.

Prosecutors said a second Saudi national, Ahmed al-Mutairi, was a mediator between Saudi officials and Twitter employees.

"The criminal complaint revealed today accuses Saudis of tampering with Twitter's internal regulations in order to obtain personal information about Saudi dissidents and thousands of platform users," US Attorney General David Anderson said.

"US laws protect American companies from such illegal foreign penetration," he said in a statement. "We will not allow US companies or technology to be used as a tool for external repression and violations of US laws."

The newspaper said the three men were accused of working with a Saudi official leading the Saudi charity organization Misk, which is run by Crown Prince Mohammed bin Salman.

She said Ali al-Zubara and Ahmed al-Mutairi were believed to be in Saudi Arabia.

The new charges come at a time when relations between the United States and Saudi Arabia remain tense over the murder of Khashoggi at his country's consulate in Istanbul on October 3, 2018.