Rights activists in Pakistan are facing "a targeted campaign of digital attacks", Amnesty International said Tuesday, the latest warning about the rising threat to campaigners in the country.

Attackers have used elaborate schemes to steal data and install spyware on Pakistani activists' electronic devices, the watchdog said in a report.

The study -- entitled "Human Rights Under Surveillance" -- is based on the experience of four activists out of a dozen cases investigated by Amnesty, the report's co-author Sherif Elsayed-Ali told AFP.

One campaigner, Diep Saeeda, said she suffered sustained harassment by hackers after calling for the release of activist Raza Khan, who fellow campaigners say was abducted from the eastern city of Lahore in December.

Saeeda told Amnesty that after she started campaigning for Khan's release, she was lured by a hacker posing as an activist on Facebook into revealing her email address.

She was then sent emails disguised as messages from government departments containing malicious links aimed at stealing her passwords and data.