Twitter has warned prominent critics of Islamic extremism that their tweets may break Pakistani law.

The social network has emailed two well-known commentators on Islam, terrorism and women’s rights to tell them that their tweeting has been complained about and could be illegal in the country.

Pakistan has previously threatened to block Twitter if the company did not remove content which the government had deemed “offensive”.

The recipients of the emails are not of Pakistani nationality or resident in Pakistan.

One of them, Saudi Arabia-born human rights activist Ensaf Haidar was contacted by Twitter’s legal department, who told her that the social network had received “official correspondence” about her account.

Her husband Raif Badawi is currently imprisoned in Saudi Arabia and has been since 2012 for apostasy, or being a non-believer.

Ms Haidar, who is not Pakistani, lives in Canada and recently gained Canadian citizenship.

The email includes a link to a tweet which Twitter says it has been told is “in violation of Pakistani law”.

The offending tweet says “retweet if you’re against niqab”, in English and French, and includes an image of a woman wearing the Islamic dress, which covers her face apart from her eyes.