Al-Azhar Observatory for Combating Terrorism has warned international online book store Amazon of the danger of publishing content that promotes extermism on its web site.

The comments by the unit of Egypt's top Islamic institution came on back of a report published by the UK newspaper The Express earlier this week which warned of the availability of these books on Amazon store although they were outlawed by the British prisons official lest that they might be the reason behind recruiting some inmates.

The report cited the Henry Jackson Society think tank as saying that several texts outlawed by prison officials in 2015 are "still available from the tech giant and are even eligible for 'next-day delivery'."

It said these include a book titled Milestones by radical ideologue abd Muslim Brotherhood leader Sayyid Qutb who was executed in 1966.

"Publishing content that promotes extremism and terrorism under the pretext of the freedom of opinion and expression is unreasonable," the observatory said, adding that hardliners and extremist groups search for any room to sneak into young people minds.

Amazon said: “As a bookseller, we provide our customers with access to a variety of viewpoints, including books that some customers may find objectionable," according to the Express.

"We reserve the right not to sell certain content, such as pornography or other inappropriate content,” Amazon added.