Saudi authorities have banned hundreds of books, including works by renowned Palestinian poet Mahmud Darwish, as part of a crackdown on publications deemed threatening to the conservative kingdom. The local Okaz daily reported Sunday that organisers at the Riyadh International Book Fair had confiscated "more than 10,000 copies of 420 books" during the exhibition. Local news website Sabq.org reported that members of the kingdom's notorious religious police had protested at "blasphemous passages" in works by the late Darwish, widely considered one of the greatest Arab poets, pressing organisers to withdraw all his books from the fair, which ended Friday. The religious police frequently intervene to enforce the kingdom's strict conservative values, but the move to ban so many works was seen as unprecedented. Similar action was taken against works by Iraq's most famous modern poet, Badr Shaker al-Sayyab, and another Iraqi poet, Abdul Wahab al-Bayati, as well as those by Palestinian poet Muin Bseiso. Activist Aziza Yousef said the crackdown had offered "free advertising to those whose books were banned" as many "rushed to download these works from the Internet." Organisers also banned all books by Azmi Bisara, a former Arab Israeli MP who fled Israel in 2007 and is now close to authorities in Qatar, where he is based, Sabq.org reported. The ban comes amid escalating tensions between Qatar and three other Gulf Arab monarchies -- Saudi Arabia, the United Arab Emirates, and Bahrain -- who pulled their envoys from Doha earlier this month, accusing it of interfering in their internal affairs. Organisers of the book fair, which began March 4, had announced ahead of the event that any book deemed "against Islam" or "undermining security" in the kingdom would be confiscated. A few days after the fair opened, Saudi authorities closed the stall of the Arab Network for Research and Publishing headed by Islamist publisher Nawaf al-Qudaimi and confiscated all his publications, citing threats to the kingdom's security.