On the occasion of the Muslim prophet's birthday last week, 23-year-old Hamza Kashgari tweeted: "I have loved things about you and I have hated things about you and there is a lot I don't understand about you."
"I will not pray for you," he added.
The controversial tweet sparked a frenzy of responses -- some 30,000, according to an online service that tracks tweets in the Arab world.
In one response, Abdullah, a lawyer, said that since Kashgari was "an adult... we should accept nothing but implementing the ruling according to Islamic law" or sharia.
Insulting the prophet is considered blasphemous in Islam, and is a crime punishable by death.
Kashgari quickly apologised for his remarks, but the calls for his execution only multiplied.