"An attack upon the Holy Prophet is an attack on the whole 1.5 billion Muslims. Therefore, this is something unacceptable," Pakistani Prime Minister Raja Pervez Ashraf said in a speech to politicians, religious leaders and others.
Pakistan has declared Friday a "Day of Love for the Prophet Mohammad". Critics of the unpopular government said it was pandering to Islamist parties.
Protesters took to the streets of the Pakistani city of Peshawar, an old frontier town on the main road to Afghanistan, and torched two cinemas and clashed with riot police who tried to disperse them with teargas.