QALQILYA, West Bank  It is hard to imagine that a dingy Internet cafe buzzing with flies in this provincial Palestinian town could have spawned a blogger who has angered the Muslim cyberworld by promoting atheism, composing spoofs of Koranic verses, skewering the lifestyle of the Prophet Muhammad and chatting online using the sarcastic Web name God Almighty.

But many people in Qalqilya seem convinced that this Facebook apostate is none other than a secretive young man who spent seven hours a day in the corner booth of a back-street hole-in-the-wall here. Until recently the man, Waleed Hasayin, in his mid-20s, led a relatively anonymous existence as an unemployed graduate in computer science who helped out a few hours a day at his father’s one-chair barber shop. Several acquaintances described him as an “ordinary guy” who prayed at the mosque on Fridays.

But since the end of October Mr. Hasayin has been detained at the local Palestinian Authority intelligence headquarters, suspected of being the blasphemous blogger who goes by the name Waleed al-Husseini. The case has drawn attention to thorny issues like freedom of expression in the Palestinian Authority, for which insulting religion is considered illegal, and the cultural collision between a conservative society and the Internet.

While Mr. Hasayin has won some admiration and support abroad  a Facebook group has formed in solidarity, along with several online petitions  others on Facebook are calling for his execution.