A former Saudi official's tweet expressing his condolences after the death of an activist seemed normal, but his disappearance in mysterious circumstances shortly thereafter highlights what human rights activists describe as the "digital authoritarianism" of the state.

Abdulaziz Al-Dakhil disappeared in April of this year, along with two well-known personalities believed to be in prison due to what were seen as criticism of the state.

Separately, information spoke about a data breach by Saudis in 2015 that led to a wave of "enforced disappearances" of critics of the regime, including people with anonymous accounts on the platform.

These cases show how Saudi Arabia, which has the largest number of Twitter users in the Arab world, has sought to use the platform's power to promote its ambitious reform plan in conjunction with its drive to curb freedom of expression.

Al-Dakhil held the position of Deputy Minister of Finance and was among three public figures believed to be in state custody.

According to human rights organizations, they disappeared last April "due to their condolences on the death of (...) Abdullah Al-Hamid."

Al-Hamid, a well-known activist, died after suffering a stroke in prison while he was serving an 11-year prison sentence, which sparked criticism from international organizations.

His son, Abdul Hakim al-Dakhil, told AFP that his father's whereabouts are unknown, and the authorities have not revealed any official charges. "Why was he taken? What was his crime?" Added his son, who is in Paris. "Was he in prison just for tweeting?"

The Saudi authorities did not respond to questions from AFP, which they contacted for comment.

- 'Simple tweet' -
Their detention comes as the Saudi authorities launch a campaign targeting activists, bloggers, and even princes in the royal family who have been arrested in recent years as Crown Prince Mohammed bin Salman seeks to strengthen his grip.

The kingdom made the arrests under a cybercrime law that human rights organizations, including Amnesty International, believe criminalize online criticism of the government.

"A simple tweet could land you in prison in Saudi Arabia without access to a lawyer for months or even years," said Lynn Maalouf, Director of Middle East Research at Amnesty International.

In 2015, a data breach on Twitter via Saudis led to unidentified critics of the government being exposed on the platform and arrested, according to families and two cases against the company.

The US Department of Justice accused former employees of spying for the Saudi government, as they accessed the data of more than six thousand accounts in search of users "critical of the regime."

According to the ministry, "the personal information of users included e-mail, phone numbers, their Internet Protocol address and their dates of birth," warning that this data could be used to locate users.

One of them was Abd al-Rahman al-Sadhan, 36, who works for the Red Crescent and expressed his views on human rights and other social issues through his anonymous Twitter account, according to his family.

His sister Areej, who lives in San Francisco, stated that he was arrested in his office in Riyadh by Saudi security in March 2018.

Two years after his disappearance, he was allowed to make a phone call to his family and said that he was being held in al-Ha'ir prison near Riyadh.

His sister confirmed to France Press, "It was his first and only call, and it lasted for less than a minute," explaining, "Someone said to him, 'The minute has ended.' There was no goodbye or I will talk to you later."

- "A weapon"-

Two Saudi dissidents in North America said in two separate lawsuits against Twitter that their accounts were targeted in the breach, endangering the lives of those close to them in Saudi Arabia.

One of the plaintiffs is Ali Al Ahmed, founder of the Gulf Institute in Washington who filed an amended complaint last August against Twitter for its "utter failure" to protect his account.

AFP saw Ahmed's lawyer on a list of eight Saudis who had contact with him through anonymous Twitter accounts, in which he says they were imprisoned, went missing, or died after the breach.

Twitter did not respond to a request for comment.

In recent years, Twitter removed thousands of "state-sponsored" Saudi accounts, citing breaching the messaging platform's policies.

According to market research firm Statica, the number of Twitter users in Saudi Arabia is about 12 million.

Electronic armies - known as "electronic flies" - are dedicated to defending the kingdom's policy and attacking critics. These armies emerged as part of a policy led by the former advisor in the royal court, Saud Al-Qahtani.

Mark Owen Jones, who wrote a book on "Digital Authoritarianism in the Middle East," says "Saudi digital authoritarianism ... is scandalous in its audacity."

"Over the past few years, entities linked to Saudi Arabia have successfully used Twitter and managed to penetrate it to the point that Twitter itself has become a weapon of authoritarian rule," Jones says.