Palestinian security forces arrested Ismat Abdul-Khaleq, a West Bank university lecturer, last Wednesday after they found writing on her Facebook page accusing President Mahmoud Abbas of being a traitor and demanding he resign, said lawyer Issam Abdeen of the Palestinian rights group al-Haq.

Abdul-Khaleq's detention is the latest in what activists say is the Palestinian authorities' increasing intolerance of criticism and a worrying trend of mining Facebook to spy on Palestinians.

We are genuinely concerned about tightening limits on freedom of expression and on the media, Abdeen said. We don't want reporters to second-guess what they write on whether they will be punished or not.

Abdeen said the Palestinian public persecutor's office was particularly harsh in ordering the prolonged detention of those accused of defamation. Abdul-Khaleq is a single mother of two children.

In other recent cases, newspaper reporter Yousef al-Shayeb has been held for eight days for allegedly defaming public officials. Al-Shayeb was expected to be released Monday after a court ordered him freed on $8,000 bail after a public outcry.

Two other reporters were interrogated last week, one for his Facebook posts and the other over a story he was researching.